CA2518942A1 - Prepreg which is produced by impregnating a base paper with a combination of resin solution and polymer dispersion - Google Patents
Prepreg which is produced by impregnating a base paper with a combination of resin solution and polymer dispersion Download PDFInfo
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- CA2518942A1 CA2518942A1 CA002518942A CA2518942A CA2518942A1 CA 2518942 A1 CA2518942 A1 CA 2518942A1 CA 002518942 A CA002518942 A CA 002518942A CA 2518942 A CA2518942 A CA 2518942A CA 2518942 A1 CA2518942 A1 CA 2518942A1
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- prepreg
- resin solution
- impregnating
- polymer dispersion
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Classifications
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
- D21H27/18—Paper- or board-based structures for surface covering
- D21H27/22—Structures being applied on the surface by special manufacturing processes, e.g. in presses
- D21H27/26—Structures being applied on the surface by special manufacturing processes, e.g. in presses characterised by the overlay sheet or the top layers of the structures
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/63—Inorganic compounds
- D21H17/70—Inorganic compounds forming new compounds in situ, e.g. within the pulp or paper, by chemical reaction with other substances added separately
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
- D21H25/04—Physical treatment, e.g. heating, irradiating
- D21H25/06—Physical treatment, e.g. heating, irradiating of impregnated or coated paper
Abstract
Disclosed are prepregs which can be obtained by impregnating a raw paper with a thermally crosslinkable impregnation combination, and methods for the production thereof. The impregnation combination contains a thermally crosslinkable, formaldehyde-free resin solution and a polymer dispersion. The mixing ratio between the resin solution and the polymer dispersion in the impregnation combination ranges between 45:55 and 10:90 (solid:solid). After drying, the prepreg has a degree of crosslinking of no less than 10 percent but no more than 85 percent and a residual moisture of 2 to 3 percent by weight. The inventive prepregs are provided with better properties than previously known formaldehyde-containing and formaldehyde-free prepregs regarding printability and surface bonding strength (ripping resistance) as early as the moment the prepregs leave the paper machine while maintaining great surface density (great ability to receive lacquer) and dimensional stability/flatness.
Description
zo Ahlstrom Osnabruck GmbH
Romereschstra(3e 33, 49090 Osnabruck Prepreg The invention relates to prepregs, to a process for their production and to decorative covering materials obtainable therefrom.
Decorative covering materials, also called decorative papers or decorative sheets, are preferably used for covering surfaces in furniture manufacture and in interior decoration, especially for laminated floors. These decorative sheets are paper webs which have been impregnated with synthetic resin and optionally surface-treated thereafter; they are decoratively printed, or unprinted, and are in a state that can no longer be reactivated under pressure and heat. Depending on the type of impregnation process, a distinction is made between thermosetting decorative sheets with a through-impregnated core (offline process) and decorative sheets based on prepregs (online process) to which a finish coating ao can then be applied. This produces a decorative sheet with a finished surface.
inside the paper machine, immediately after sheet forming and drying, decorative sheets based on prepregs are impregnated with a resin mixture to a greater or lesser depth, depending on the mass per unit area of the base paper. After drying as and smoothing, usually also inside the paper machine, the paper or sheet must be crosslinked and hence acquire interlaminar strength so that no fibre separation occurs within the decorative sheet during the subsequent processing steps of finish-coating and lamination onto appropriate substrates. Moreover, for further processing, the prepregs are required to have a high covering power and surface quality, a good printability in rotogravure, a good varnishability (high varnish resistance), a good flatness and the ability to be glued to chipboard and MDF (medium density fibreboard).
The thermally crosslinkable impregnating resins conventionally used for the production of prepregs are water-thinnable, formaldehyde-containing resin 1o solutions based on urea-formaldehyde, melamine-formaldehyde or phenol-formaldehyde resins. Because use of these resin solutions on their own results in relatively brittle products, they are generally used in combination with water-thinnable, thermally crosslinkable polymer dispersions based on acrylic acid, acrylic acid ester, styrene, butadiene, vinyl acetate or acrylonitrile.
The resin uptake in the case of prepregs can be between 5 and 35 wt.%, the resin solution component generally penetrating deeper into the base paper than the polymer dispersion component. The polymer dispersions concentrate to a greater or lesser extent on the top side and bottom side of the paper and ensure 2o that the papers have a good smoothability and hence printability, as well as surface imperviousness and hence varnishability (varnish resistance). The resin solutions, on the other hand, are intended to ensure the good interlaminar strength and flatness of the prepreg by crosslinking of the fibre-resin composite during further processing.
The penetration depth of polymer dispersions can be increased by a variety of additives, e.g. water-soluble polymers based on polyvinyl alcohols, gelatin, starches, cellulose derivatives, alginates and mixtures thereof (EP 0 739 435 B1 ), malefic acid copolymers (EP 0 223 922 A1 ) or a (meth)acrylamide/(meth)acrylic so acid copolymer (DE 197 28 250 A1 and DE 197 58 479 A1 ).
In some cases, when producing the prepregs using the above-mentioned additives, the use of conventional formaldehyde-containing resin solutions is dispensed with altogether. However, these now formaldehyde-free prepregs have a limited interlaminar strength, flatness and printability.
These disadvantages are avoided by using a thermosetting, formaldehyde-free resin solution which does not crosslink extensively until the prepreg is heat-treated for a period of about 40 seconds at about 132°C according to DE
302 C1 (maximum degree of crosslinking of 85%). The resin solution used for this purpose, whose preparation and possible uses, inter alia for the impregnation of papers for decorative applications, are described in DE 197 35 959 A1. The ~o disadvantage is that the internal strengths of such a prepreg according to 34 302 C2, which is completely uncrosslinked until it is hot-pressed on the substrate material (e.g. chipboard) as the last further processing step, are currently no better, or even poorer, than those of known formaldehyde-free or formaldehyde-containing prepregs. In particular, until it is hot-pressed, it has a is poorer surface imperviousness and hence poorer varnishability (lower varnish resistance), as well as a poorer flatness during lamination (gluing), than formaldehyde-free and formaldehyde-containing prepregs known hitherto.
The object of the invention is therefore to provide partially crosslinked prepregs 2o which already extensively avoid said disadvantages by the time they reach the end of the paper machine, which, as far as possible, are distinguished by a high surface quality, a good printability and a higher interlaminar strength than that of known formaldehyde-free or formaldehyde-containing prepregs, a good varnishabifity (high varnish resistance), a good flatness and the ability to be glued 25 with conventional adhesives in the subsequent processing stages, and whose properties are thus almost equivalent to those of offline-impregnated papers.
This object is achieved by a formaldehyde-free prepreg having the characteristics according to Claim 1. Other advantageous embodiments are given in the so subordinate claims.
As far as the process is concerned, the object is achieved by a process according to Claim 8, other advantageous embodiments being given in the corresponding subordinate claims.
Romereschstra(3e 33, 49090 Osnabruck Prepreg The invention relates to prepregs, to a process for their production and to decorative covering materials obtainable therefrom.
Decorative covering materials, also called decorative papers or decorative sheets, are preferably used for covering surfaces in furniture manufacture and in interior decoration, especially for laminated floors. These decorative sheets are paper webs which have been impregnated with synthetic resin and optionally surface-treated thereafter; they are decoratively printed, or unprinted, and are in a state that can no longer be reactivated under pressure and heat. Depending on the type of impregnation process, a distinction is made between thermosetting decorative sheets with a through-impregnated core (offline process) and decorative sheets based on prepregs (online process) to which a finish coating ao can then be applied. This produces a decorative sheet with a finished surface.
inside the paper machine, immediately after sheet forming and drying, decorative sheets based on prepregs are impregnated with a resin mixture to a greater or lesser depth, depending on the mass per unit area of the base paper. After drying as and smoothing, usually also inside the paper machine, the paper or sheet must be crosslinked and hence acquire interlaminar strength so that no fibre separation occurs within the decorative sheet during the subsequent processing steps of finish-coating and lamination onto appropriate substrates. Moreover, for further processing, the prepregs are required to have a high covering power and surface quality, a good printability in rotogravure, a good varnishability (high varnish resistance), a good flatness and the ability to be glued to chipboard and MDF (medium density fibreboard).
The thermally crosslinkable impregnating resins conventionally used for the production of prepregs are water-thinnable, formaldehyde-containing resin 1o solutions based on urea-formaldehyde, melamine-formaldehyde or phenol-formaldehyde resins. Because use of these resin solutions on their own results in relatively brittle products, they are generally used in combination with water-thinnable, thermally crosslinkable polymer dispersions based on acrylic acid, acrylic acid ester, styrene, butadiene, vinyl acetate or acrylonitrile.
The resin uptake in the case of prepregs can be between 5 and 35 wt.%, the resin solution component generally penetrating deeper into the base paper than the polymer dispersion component. The polymer dispersions concentrate to a greater or lesser extent on the top side and bottom side of the paper and ensure 2o that the papers have a good smoothability and hence printability, as well as surface imperviousness and hence varnishability (varnish resistance). The resin solutions, on the other hand, are intended to ensure the good interlaminar strength and flatness of the prepreg by crosslinking of the fibre-resin composite during further processing.
The penetration depth of polymer dispersions can be increased by a variety of additives, e.g. water-soluble polymers based on polyvinyl alcohols, gelatin, starches, cellulose derivatives, alginates and mixtures thereof (EP 0 739 435 B1 ), malefic acid copolymers (EP 0 223 922 A1 ) or a (meth)acrylamide/(meth)acrylic so acid copolymer (DE 197 28 250 A1 and DE 197 58 479 A1 ).
In some cases, when producing the prepregs using the above-mentioned additives, the use of conventional formaldehyde-containing resin solutions is dispensed with altogether. However, these now formaldehyde-free prepregs have a limited interlaminar strength, flatness and printability.
These disadvantages are avoided by using a thermosetting, formaldehyde-free resin solution which does not crosslink extensively until the prepreg is heat-treated for a period of about 40 seconds at about 132°C according to DE
302 C1 (maximum degree of crosslinking of 85%). The resin solution used for this purpose, whose preparation and possible uses, inter alia for the impregnation of papers for decorative applications, are described in DE 197 35 959 A1. The ~o disadvantage is that the internal strengths of such a prepreg according to 34 302 C2, which is completely uncrosslinked until it is hot-pressed on the substrate material (e.g. chipboard) as the last further processing step, are currently no better, or even poorer, than those of known formaldehyde-free or formaldehyde-containing prepregs. In particular, until it is hot-pressed, it has a is poorer surface imperviousness and hence poorer varnishability (lower varnish resistance), as well as a poorer flatness during lamination (gluing), than formaldehyde-free and formaldehyde-containing prepregs known hitherto.
The object of the invention is therefore to provide partially crosslinked prepregs 2o which already extensively avoid said disadvantages by the time they reach the end of the paper machine, which, as far as possible, are distinguished by a high surface quality, a good printability and a higher interlaminar strength than that of known formaldehyde-free or formaldehyde-containing prepregs, a good varnishabifity (high varnish resistance), a good flatness and the ability to be glued 25 with conventional adhesives in the subsequent processing stages, and whose properties are thus almost equivalent to those of offline-impregnated papers.
This object is achieved by a formaldehyde-free prepreg having the characteristics according to Claim 1. Other advantageous embodiments are given in the so subordinate claims.
As far as the process is concerned, the object is achieved by a process according to Claim 8, other advantageous embodiments being given in the corresponding subordinate claims.
The prepreg according to the invention can be obtained by impregnating a base paper with an impregnating combination containing a thermosetting, formaldehyde-free resin solution and a thermally crosslinkable polymer dispersion. The impregnated base paper is dried and smoothed, the smoothing expediently taking place inside the paper machine used to produce the prepreg.
The degree of crosslinking of the prepreg is at least 10% and at most 85%. The impregnated base paper has a residual moisture content of 2 to 3 wt.%.
~o The degree of crosslinking is determined analogously to the test method described in DE 101 34 302 C1, wherein an area of 100 cm2 of prepreg is stamped out, weighed, kept in water at a temperature of 60°C for 15 min, rinsed, dried in the oven at 130°C and weighed again. The soluble proportion of the polymers) can be determined from the weight difference and the known i5 application rate of the impregnating resin or impregnating combination (e.g. 12 g/mz dry, for a 60 g/m2 prepreg). The degree of crosslinking in % is then 100 -soluble proportion in %.
The invention also provides a process for the production of thermally partially 2o crosslinked, formaldehyde-free prepregs inside the paper machine and to their use as decorative covering materials. Prepregs are understood according to the invention as meaning papers partially impregnated with formaldehyde-free resin solutions in combination with polymer dispersions. The proportion of impregnating components is 5 to 35 wt.%, preferably 10 to 30 wt.%, based on the 25 base paper weight.
The residual moisture content of the prepreg is between 1.5 and 3 wt.%.
Residual moisture contents of more than 3.5 wt.% can cause the prepreg to stick to machine parts, for example the smoothing rolls of the paper machine.
Formaldehyde-free resin solutions suitable for impregnation are the polymer compositions described in DE 197 35 959 A1 and containing A) at least one polymer obtainable by free-radical polymerization and containing less than 5 wt.% of an a,~i-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, B) at least one polymer obtainable by free-radical polymerization and containing more than 15 wt.% of an a,(i-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, and C) at least one alkanolamine having at least two hydroxyl groups.
In one particularly preferred embodiment, the base paper can be impregnated using a resin that contains afore-mentioned components B) and C), but not component A). Such resins are disclosed in DE 197 35 959 A1.
The water-thinnable impregnating mixture according to the invention, consisting of above-mentioned formaldehyde-free resin solutions A) + B) + C) or B) + C) and conventionally used polymer dispersions, is applied to at least one side of zo the paper web, then dried to a residual moisture content of 2 to 3 wt.% and then smoothed. The impregnated base paper is thereby partially crosslinked, the degree of crosslinking being between at least 10% and max. 85%, depending on the mixing ratios of the impregnating combination. In the subsequent processing steps, such as printing, varnishing and lamination/gluing, this only partially crosslinked prepreg is sufficiently flexible. It is particularly advantageous for the quality of the prepreg if the residual moisture content is already adjusted in the paper machine (online). In line with the general usage of the term, a paper machine is understood as meaning the paper production unit from the screening of the fibre suspension to the rolling-up of the base paper.
The mixing ratio of formaldehyde-free resin solution (I) to polymer dispersion (II) can be 49:51 to 10:90 (solidaolid), preferably 45:55 to 20:80. Particularly preferred mixing ratios are from 35:65 to 30:70 because prepregs produced with impregnating combinations having these mixing ratios have a particularly good printability and adequate flexibility.
The concentration of the impregnating mixture according to the invention, which s contains further additives if necessary, can be up to 50 wt.%. The impregnating combination according to the invention can be applied to the paper web online in an amount of between 5 and 35 wt.%, preferably of between 10 and 30 wt.%, based on the weight per unit area of the base paper. The application devices employed can be any units conventionally used inside the paper machine, ~o preferably roller application devices such as a size press or film press.
Surprisingly, it has been found that the prepregs according to the invention have better properties than already known formaldehyde-containing and formaldehyde-free prepregs in respect of printability and surface strength (tesa is strength), even immediately on leaving the paper machine. At the same time, however, they retain a high surface imperviousness (high lacquer resistance) and dimensional stability/flatness which formaldehyde-free, uncrosslinked prepregs according to DE 101 34 302 C1, i.e. impregnated with the above-mentioned formaldehyde-free resin solutions according to DE 197 35 959 A1, do not 2o possess on leaving the paper machine. In the case of the last-mentioned prepreg, partial crosslinking only takes place at the end of the entire further processing chain, i.e. during hot pressing.
These outstanding properties of the prepreg according to the invention are 25 achieved by combining resin solutions and polymer dispersions in a particular mixing ratio for which an optimum is established between the penetrating and film-forming properties of the individual components on impregnation of the base paper, and which has already extensively reached its final state inside the paper machine, presumably due to synergistic effects and the influence of temperature.
The prepreg according to the invention can therefore be used in a significantly more universal manner in the further processing steps and is not subject to any technological limitations in respect of different process parameters such as speed, temperature and pressure. In particular, the prepregs according to the invention can be produced so as to possess a high flexibility, dimensional stability and good barrier properties against water and solvents and can be used in particular as a base material for high-quality special papers such as printing and advertising substrates, decorative wall materials, abrasive papers, adhesive s tapes or floor coverings.
It has been possible to achieve particularly good grades of prepreg when its degree of crosslinking is more than 50% and preferably 70% or more.
~o The base papers to be impregnated according to the invention are those described inter alia in patents EP 0 223 922 A1, EP 0 870 872 A1 and DE 101 34 302 A1. Likewise, the corresponding impregnation, drying and smoothing processes are described in detail in said documents and in the journal "Wochenblatt fur Papierfabrikation" no. 6 (2000), pp 350 to 355, and are known ~s state of the art.
The Examples which follow illustrate the invention. Unless stated otherwise, all amounts are based on the solid or solids content.
2o Example 1 (Comparative) A base paper consisting of 20% of kraft pulp and 80% of eucalyptus pulp was produced according to the invention. The freeness value was 30°SR
(Schopper-Riegler). The additives used were 25% of titanium dioxide and 4% of 25 formaldehyde-free wet strength additive, based on absolutely dry pulp. This base paper, without internal sizing and with a weight per unit area of 48 g/m2, was impregnated on both sides in a laboratory size press with a formaldehyde-free resin solution of modified polyacrylic acid and a polyhydric alcohol (Acrodur from BASF), having a solids content of approx. 30%, and then dried at different so temperatures for approx. 18 seconds to a residual moisture content of approx.
2%.
The application rate after drying was 10 g/m2.
_$-The degrees of crosslinking of the prepregs dried at different temperatures are collated in Table 1. A partial crosslinking of the prepregs to about 30% then takes place under drying conditions that are conventionally used in the paper machine (up to 110°C, drying time approx. 14 seconds at 300 m/min).
Example 2,IPrenreg according to the invention) The base paper from Example 1 was impregnated by means of a laboratory size press with the impregnating mixture according to the invention, consisting of a ~o formaldehyde-free resin solution (Acrodur 950 L) and a styrene/acrylate dispersion (Acronal 305 D from BASF) in a ratio of 35:65 (solidaolid), and dried for approx. 18 seconds at temperatures of about 110°C to a residual moisture content of approx. 2%.
is The application rate was about 12 g/m2. The degree of crosslinking of the prepreg according to the invention was approx. 70%. Accordingly, the addition of polymer dispersion to the resin solution significantly increases the degree of crosslinking.
2o Example 3 (Comparative) The base paper from Example 1 was impregnated by means of a laboratory size press with an impregnating mixture conventionally used for prepregs, consisting of formaldehyde-free styrene/acrylate dispersion (Acronal 305) and 2s formaldehyde-containing resin solution (Urecoll TS) in a ratio of 70:30 (A) and 90:10 (B) (based on solids), and then dried analogously to Example 2. The application rate was approx. 13 glm2 in each case.
The degree of crosslinking of the conventional prepreg was 76% (A) or 84% (B), so i.e. significantly higher than that of prepregs according to the invention containing formaldehyde-free resin solutions according to Examples 1 and 2.
_g_ Example 4 The prepregs produced according to Examples 1 to 3 were smoothed under constant conditions in a laboratory calender. The paper properties achieved are collated in Table 2.
In comparison with conventionally used formaldehyde-containing or low-formaldehyde prepregs (Comparative Examples 3 A and 3 B), the formaldehyde-free prepreg according to the invention (Example 2) has a significantly better ~o interlaminar strength and printability. The lacquer resistance remains at a high quality level, while the flatness deteriorates somewhat.
In contrast to the formaldehyde-free prepreg according to Example 1, the prepreg according to the invention (Example 2) is distinguished by an improved surface ~5 imperviousness and hence a significantly higher lacquer resistance, lower colour bleeding (pinhole test) and better printability, as well as a greater flatness.
The significantly better properties of the thermally partially crosslinked prepreg according to the invention are due to the combination of resin solution and 2o polymer dispersion in a specific range of mixing ratios, and the consequently higher degrees of crosslinking than with the resin solution alone.
Table 1 Degree of crosslinking of prepregs after different heat treatments (contact drying) Drying temperature, C
Degree of crosslinking, % 0 11.3 18.6 30.5 Impregnation with formaldehyde-free resin solution so Acrodur 350 L, 30%
Application rate approx. 10 g/m2 O
O
O w O
O N ~ ~ O
d "G
_ O N 00 N
a V O O O M etN ~ ~' r N r p t >
c0 ~ Q Q O. N r ~"~ OO V
C
d 41 LIJR !0A
~s aw d o a w w O O r (~
_ X X X ~ O l!~ O N
d 'O ~ O O O h ~ O COr' r d''~ O
O
O (0d d d M N N N V
~ O
O
W c~ ca O
O
d N
a C m O f~~ ~~~JL
O CDr OO N
O
O O O ~
~ ~ O ~ ~ tI~~ r M X
d M
~
i N d d Q N O
- ~ ~ a a a ~ o ~ o U ~ m m m ~ 3 ' ~ ~ o a~
a L
Q
n Q
O M Cp M O r ~ O
C O r CO
' D ~ O O ~ i~O T ~ '~r C'~ O
~' 'L . a a a '-M N O d ~
O. X f0(~(B
W
O
C
Q1~ 07~ U7fn O
L
OO
~
a ~ o c o ~ ~ ~ o >
>
p_~p c .p L ~ ~ ~ II
II
C C ~ ~ _ O j ' r-O Lf~
~p O C = C U
. N N
~
....aj~ ~ O tn~ ~ ~ ' ' : O .-~
_.
~ o ~ . ~ ~n ~n o ~ t o U O a o .-. ~ O O 7, O ~ V ~ C ~ ~ ~ L
Q O C O ~ .-.
faO ~ ~ ~ N ~ U N
O ~
Q m O C Y ~
4: U C w _ _f~. C_ D O
~ r ~ c :
Q m m u. ~ d 4.~ LL
The degree of crosslinking of the prepreg is at least 10% and at most 85%. The impregnated base paper has a residual moisture content of 2 to 3 wt.%.
~o The degree of crosslinking is determined analogously to the test method described in DE 101 34 302 C1, wherein an area of 100 cm2 of prepreg is stamped out, weighed, kept in water at a temperature of 60°C for 15 min, rinsed, dried in the oven at 130°C and weighed again. The soluble proportion of the polymers) can be determined from the weight difference and the known i5 application rate of the impregnating resin or impregnating combination (e.g. 12 g/mz dry, for a 60 g/m2 prepreg). The degree of crosslinking in % is then 100 -soluble proportion in %.
The invention also provides a process for the production of thermally partially 2o crosslinked, formaldehyde-free prepregs inside the paper machine and to their use as decorative covering materials. Prepregs are understood according to the invention as meaning papers partially impregnated with formaldehyde-free resin solutions in combination with polymer dispersions. The proportion of impregnating components is 5 to 35 wt.%, preferably 10 to 30 wt.%, based on the 25 base paper weight.
The residual moisture content of the prepreg is between 1.5 and 3 wt.%.
Residual moisture contents of more than 3.5 wt.% can cause the prepreg to stick to machine parts, for example the smoothing rolls of the paper machine.
Formaldehyde-free resin solutions suitable for impregnation are the polymer compositions described in DE 197 35 959 A1 and containing A) at least one polymer obtainable by free-radical polymerization and containing less than 5 wt.% of an a,~i-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, B) at least one polymer obtainable by free-radical polymerization and containing more than 15 wt.% of an a,(i-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, and C) at least one alkanolamine having at least two hydroxyl groups.
In one particularly preferred embodiment, the base paper can be impregnated using a resin that contains afore-mentioned components B) and C), but not component A). Such resins are disclosed in DE 197 35 959 A1.
The water-thinnable impregnating mixture according to the invention, consisting of above-mentioned formaldehyde-free resin solutions A) + B) + C) or B) + C) and conventionally used polymer dispersions, is applied to at least one side of zo the paper web, then dried to a residual moisture content of 2 to 3 wt.% and then smoothed. The impregnated base paper is thereby partially crosslinked, the degree of crosslinking being between at least 10% and max. 85%, depending on the mixing ratios of the impregnating combination. In the subsequent processing steps, such as printing, varnishing and lamination/gluing, this only partially crosslinked prepreg is sufficiently flexible. It is particularly advantageous for the quality of the prepreg if the residual moisture content is already adjusted in the paper machine (online). In line with the general usage of the term, a paper machine is understood as meaning the paper production unit from the screening of the fibre suspension to the rolling-up of the base paper.
The mixing ratio of formaldehyde-free resin solution (I) to polymer dispersion (II) can be 49:51 to 10:90 (solidaolid), preferably 45:55 to 20:80. Particularly preferred mixing ratios are from 35:65 to 30:70 because prepregs produced with impregnating combinations having these mixing ratios have a particularly good printability and adequate flexibility.
The concentration of the impregnating mixture according to the invention, which s contains further additives if necessary, can be up to 50 wt.%. The impregnating combination according to the invention can be applied to the paper web online in an amount of between 5 and 35 wt.%, preferably of between 10 and 30 wt.%, based on the weight per unit area of the base paper. The application devices employed can be any units conventionally used inside the paper machine, ~o preferably roller application devices such as a size press or film press.
Surprisingly, it has been found that the prepregs according to the invention have better properties than already known formaldehyde-containing and formaldehyde-free prepregs in respect of printability and surface strength (tesa is strength), even immediately on leaving the paper machine. At the same time, however, they retain a high surface imperviousness (high lacquer resistance) and dimensional stability/flatness which formaldehyde-free, uncrosslinked prepregs according to DE 101 34 302 C1, i.e. impregnated with the above-mentioned formaldehyde-free resin solutions according to DE 197 35 959 A1, do not 2o possess on leaving the paper machine. In the case of the last-mentioned prepreg, partial crosslinking only takes place at the end of the entire further processing chain, i.e. during hot pressing.
These outstanding properties of the prepreg according to the invention are 25 achieved by combining resin solutions and polymer dispersions in a particular mixing ratio for which an optimum is established between the penetrating and film-forming properties of the individual components on impregnation of the base paper, and which has already extensively reached its final state inside the paper machine, presumably due to synergistic effects and the influence of temperature.
The prepreg according to the invention can therefore be used in a significantly more universal manner in the further processing steps and is not subject to any technological limitations in respect of different process parameters such as speed, temperature and pressure. In particular, the prepregs according to the invention can be produced so as to possess a high flexibility, dimensional stability and good barrier properties against water and solvents and can be used in particular as a base material for high-quality special papers such as printing and advertising substrates, decorative wall materials, abrasive papers, adhesive s tapes or floor coverings.
It has been possible to achieve particularly good grades of prepreg when its degree of crosslinking is more than 50% and preferably 70% or more.
~o The base papers to be impregnated according to the invention are those described inter alia in patents EP 0 223 922 A1, EP 0 870 872 A1 and DE 101 34 302 A1. Likewise, the corresponding impregnation, drying and smoothing processes are described in detail in said documents and in the journal "Wochenblatt fur Papierfabrikation" no. 6 (2000), pp 350 to 355, and are known ~s state of the art.
The Examples which follow illustrate the invention. Unless stated otherwise, all amounts are based on the solid or solids content.
2o Example 1 (Comparative) A base paper consisting of 20% of kraft pulp and 80% of eucalyptus pulp was produced according to the invention. The freeness value was 30°SR
(Schopper-Riegler). The additives used were 25% of titanium dioxide and 4% of 25 formaldehyde-free wet strength additive, based on absolutely dry pulp. This base paper, without internal sizing and with a weight per unit area of 48 g/m2, was impregnated on both sides in a laboratory size press with a formaldehyde-free resin solution of modified polyacrylic acid and a polyhydric alcohol (Acrodur from BASF), having a solids content of approx. 30%, and then dried at different so temperatures for approx. 18 seconds to a residual moisture content of approx.
2%.
The application rate after drying was 10 g/m2.
_$-The degrees of crosslinking of the prepregs dried at different temperatures are collated in Table 1. A partial crosslinking of the prepregs to about 30% then takes place under drying conditions that are conventionally used in the paper machine (up to 110°C, drying time approx. 14 seconds at 300 m/min).
Example 2,IPrenreg according to the invention) The base paper from Example 1 was impregnated by means of a laboratory size press with the impregnating mixture according to the invention, consisting of a ~o formaldehyde-free resin solution (Acrodur 950 L) and a styrene/acrylate dispersion (Acronal 305 D from BASF) in a ratio of 35:65 (solidaolid), and dried for approx. 18 seconds at temperatures of about 110°C to a residual moisture content of approx. 2%.
is The application rate was about 12 g/m2. The degree of crosslinking of the prepreg according to the invention was approx. 70%. Accordingly, the addition of polymer dispersion to the resin solution significantly increases the degree of crosslinking.
2o Example 3 (Comparative) The base paper from Example 1 was impregnated by means of a laboratory size press with an impregnating mixture conventionally used for prepregs, consisting of formaldehyde-free styrene/acrylate dispersion (Acronal 305) and 2s formaldehyde-containing resin solution (Urecoll TS) in a ratio of 70:30 (A) and 90:10 (B) (based on solids), and then dried analogously to Example 2. The application rate was approx. 13 glm2 in each case.
The degree of crosslinking of the conventional prepreg was 76% (A) or 84% (B), so i.e. significantly higher than that of prepregs according to the invention containing formaldehyde-free resin solutions according to Examples 1 and 2.
_g_ Example 4 The prepregs produced according to Examples 1 to 3 were smoothed under constant conditions in a laboratory calender. The paper properties achieved are collated in Table 2.
In comparison with conventionally used formaldehyde-containing or low-formaldehyde prepregs (Comparative Examples 3 A and 3 B), the formaldehyde-free prepreg according to the invention (Example 2) has a significantly better ~o interlaminar strength and printability. The lacquer resistance remains at a high quality level, while the flatness deteriorates somewhat.
In contrast to the formaldehyde-free prepreg according to Example 1, the prepreg according to the invention (Example 2) is distinguished by an improved surface ~5 imperviousness and hence a significantly higher lacquer resistance, lower colour bleeding (pinhole test) and better printability, as well as a greater flatness.
The significantly better properties of the thermally partially crosslinked prepreg according to the invention are due to the combination of resin solution and 2o polymer dispersion in a specific range of mixing ratios, and the consequently higher degrees of crosslinking than with the resin solution alone.
Table 1 Degree of crosslinking of prepregs after different heat treatments (contact drying) Drying temperature, C
Degree of crosslinking, % 0 11.3 18.6 30.5 Impregnation with formaldehyde-free resin solution so Acrodur 350 L, 30%
Application rate approx. 10 g/m2 O
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Claims (14)
1. Prepreg obtainable by impregnating a base paper with a thermally crosslinkable impregnating combination containing a formaldehyde-free resin solution and a polymer dispersion, characterized in that the mixing ratio of resin solution to polymer dispersion in the impregnating combination is 45:55 to 10:90 (solid:solid), the residual moisture content is 2 to 3 wt.% and the prepreg has a degree of crosslinking of at least 10% and at most 85% after drying.
2. Prepreg according to Claim 1 wherein the resin solution contains:
a) a polymer obtainable by free-radical polymerization and containing less than 5 wt.% of an .alpha.,.beta.-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, b) a polymer obtainable by free-radical polymerization and containing more than 15 wt.% of an .alpha.,.beta.-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, and c) an alkanolamine having at least two hydroxyl groups.
a) a polymer obtainable by free-radical polymerization and containing less than 5 wt.% of an .alpha.,.beta.-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, b) a polymer obtainable by free-radical polymerization and containing more than 15 wt.% of an .alpha.,.beta.-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, and c) an alkanolamine having at least two hydroxyl groups.
3. Prepreg according to Claim 1 or 2, characterized in that the polymer dispersion is based on acrylic acid, acrylic acid ester, styrene, butadiene, vinyl acetate or acrylonitrile.
4. Prepreg according to one of Claims 1 to 3, characterized in that the mixing ratio of resin solution to polymer dispersion in the impregnating combination is 35:65 to 30:70.
5. Prepreg according to one of Claims 1 to 4, characterized in that the proportion of impregnating components in the paper is between 5 and 35 wt.%, based on the weight per unit area of the base paper.
6. Prepreg according to one of Claims 1 to 5, characterized in that drying takes place up to a residual moisture content of 2 to 3 wt.%, the resulting degrees of crosslinking being at least 50%, preferably at least 70%.
7. Prepreg according to one of Claims 1 to 6, characterized in that it is a decorative prepreg or decorative covering material.
8. Process for the production of a prepreg, comprising the following steps:
a) impregnation of a base paper with a thermally crosslinkable impregnating combination containing a formaldehyde-free resin solution and a polymer dispersion, the mixing ratio of resin solution to polymer dispersion in the impregnating combination being 45:55 to 10:90 (solid:solid), and b) drying of the impregnated base paper so that the impregnating combination has a degree of crosslinking of at least 10% and at most 85% and a residual moisture content of 2 to 3 wt.%.
a) impregnation of a base paper with a thermally crosslinkable impregnating combination containing a formaldehyde-free resin solution and a polymer dispersion, the mixing ratio of resin solution to polymer dispersion in the impregnating combination being 45:55 to 10:90 (solid:solid), and b) drying of the impregnated base paper so that the impregnating combination has a degree of crosslinking of at least 10% and at most 85% and a residual moisture content of 2 to 3 wt.%.
9. Process according to Claim 8, characterized in that the resin solution contains:
a) a polymer obtainable by free-radical polymerization and containing less than 5 wt.% of an .alpha.,.beta.-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, b) a polymer obtainable by free-radical polymerization and containing more than 15 wt.% of an .alpha.,.beta.-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, and c) an alkanolamine having at least two hydroxyl groups.
a) a polymer obtainable by free-radical polymerization and containing less than 5 wt.% of an .alpha.,.beta.-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, b) a polymer obtainable by free-radical polymerization and containing more than 15 wt.% of an .alpha.,.beta.-ethylenically unsaturated monocarboxylic or dicarboxylic acid incorporated during polymerization, and c) an alkanolamine having at least two hydroxyl groups.
10. Process according to Claim 8 or 9, characterized in that drying is carried out at 100°C or above.
11. Process according to one of Claims 8 to 10, characterized in that, on impregnation, the mixing ratio of resin solution to polymer dispersion in the impregnating combination is 35:65 to 30:70.
12. Process according to one of Claims 8 to 11, characterized in that, on impregnation, the proportion of impregnating components in the paper is between and 35 wt.%, based on the weight per unit area of the base paper.
13. Process according to one of Claims 8 to 12, characterized in that drying takes place in the paper machine.
14. Process according to one of Claims 8 to 13, characterized in that the impregnating combination, the resin solution and/or the polymer dispersion are applied to the base paper by means of a roller application device, preferably a size press or film press.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE10307966A DE10307966C5 (en) | 2003-02-24 | 2003-02-24 | Preimpregnate and process for its preparation |
| DE10307966.1 | 2003-02-24 | ||
| PCT/EP2004/001393 WO2004074577A1 (en) | 2003-02-24 | 2004-02-13 | Prepreg |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2518942A1 true CA2518942A1 (en) | 2004-09-02 |
| CA2518942C CA2518942C (en) | 2014-08-05 |
Family
ID=32841851
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2518942A Expired - Fee Related CA2518942C (en) | 2003-02-24 | 2004-02-13 | Prepreg which is produced by impregnating a base paper with a combination of resin solution and polymer dispersion |
Country Status (7)
| Country | Link |
|---|---|
| EP (2) | EP1757731A3 (en) |
| AT (1) | ATE338167T1 (en) |
| BR (1) | BRPI0407760B1 (en) |
| CA (1) | CA2518942C (en) |
| DE (2) | DE10307966C5 (en) |
| ES (1) | ES2271845T5 (en) |
| WO (1) | WO2004074577A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7968637B2 (en) | 2006-12-22 | 2011-06-28 | Rohm And Haas Company | Curable composition |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7909397B2 (en) | 2003-05-15 | 2011-03-22 | Audiovox Corporation | In-vehicle docking station for a portable media player |
| PT2222922T (en) * | 2007-12-17 | 2017-09-11 | Schoeller Technocell Gmbh & Co Kg | Compressible decorative paper impregnating agent which can be printed by the inkjet method |
| DE102008014558A1 (en) | 2008-03-15 | 2009-09-17 | Dracowo Forschungs- Und Entwicklungs Gmbh | Polycarboxylic acid modified native epoxides with a specific ratio of epoxide-polycarboxylic acid in glycidyl ester epoxide, useful for preparing polyether and polyester |
| PL2695745T3 (en) | 2012-08-06 | 2016-03-31 | Unilin Bvba | Method for manufacturing panels having a decorative surface |
| DE102013114420A1 (en) | 2012-12-23 | 2014-06-26 | Michael Jokiel | Impregnated paper comprises base paper which is impregnated on one side with water-based impregnating solution comprising e.g. aqueous dispersion of styrene-ethyl-butyl acrylate copolymer and aqueous dispersion of styrene-acrylate copolymer |
| EP2894047B1 (en) | 2014-01-10 | 2019-08-14 | Unilin, BVBA | Method for manufacturing panels having a decorative surface |
| ES2762235T3 (en) | 2014-02-06 | 2020-05-22 | Unilin Bvba | Manufacturing procedure for floor panels having a decorative surface |
| BE1025875B1 (en) | 2018-01-04 | 2019-08-06 | Unilin Bvba | Methods for manufacturing panels |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2949306A1 (en) † | 1979-12-07 | 1981-06-11 | Letron GmbH, 8750 Aschaffenburg | Synthetic veneer of paper fibre compsn. impregnated with resin - contg. equal wt. of long and short fibres, can be made on paper machine |
| FR2692584B1 (en) * | 1992-06-22 | 1994-08-26 | Buhl Papierfabrick Gmb Geb | New impregnation composition for decorative sheets for the production of laminated panels. |
| EP0739435B1 (en) * | 1993-12-21 | 1998-10-28 | Arjo Wiggins S.A. | Impregnated paper sheet as decorative overlay |
| DE19728250C2 (en) * | 1997-07-02 | 2002-01-17 | Koehler Decor Gmbh & Co Kg | Process for producing a pre-impregnate, the pre-impregnate obtained therewith and its use for the production of decorative composite structures |
| DE19735959A1 (en) † | 1997-08-19 | 1999-02-25 | Basf Ag | Thermally curable, aqueous binding agent composition |
| DE10134302C1 (en) * | 2001-07-14 | 2002-12-12 | Technocell Dekor Gmbh & Co Kg | Pre-impregnate obtained by impregnation of crude paper with a thermally hardenable formaldehyde-free resin useful in the production of decorative impregnates or coatings, and surface treatment of printed and unprinted papers |
| US20040039098A1 (en) * | 2002-08-22 | 2004-02-26 | Hector Belmares | Formaldehyde-free coatings and acoustical panel |
-
2003
- 2003-02-24 DE DE10307966A patent/DE10307966C5/en not_active Expired - Fee Related
-
2004
- 2004-02-13 ES ES04710840T patent/ES2271845T5/en not_active Expired - Lifetime
- 2004-02-13 EP EP06119238A patent/EP1757731A3/en not_active Withdrawn
- 2004-02-13 EP EP04710840.2A patent/EP1518024B2/en not_active Expired - Lifetime
- 2004-02-13 DE DE502004001322T patent/DE502004001322D1/en not_active Expired - Lifetime
- 2004-02-13 BR BRPI0407760-1A patent/BRPI0407760B1/en not_active IP Right Cessation
- 2004-02-13 AT AT04710840T patent/ATE338167T1/en not_active IP Right Cessation
- 2004-02-13 CA CA2518942A patent/CA2518942C/en not_active Expired - Fee Related
- 2004-02-13 WO PCT/EP2004/001393 patent/WO2004074577A1/en active IP Right Grant
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7968637B2 (en) | 2006-12-22 | 2011-06-28 | Rohm And Haas Company | Curable composition |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2518942C (en) | 2014-08-05 |
| BRPI0407760A (en) | 2006-10-03 |
| EP1518024B1 (en) | 2006-08-30 |
| DE10307966B4 (en) | 2005-08-11 |
| EP1518024A1 (en) | 2005-03-30 |
| WO2004074577A1 (en) | 2004-09-02 |
| DE10307966A1 (en) | 2004-09-09 |
| ES2271845T5 (en) | 2013-11-22 |
| EP1518024B2 (en) | 2013-08-07 |
| DE10307966C5 (en) | 2009-05-28 |
| DE502004001322D1 (en) | 2006-10-12 |
| BRPI0407760B1 (en) | 2014-04-22 |
| EP1757731A3 (en) | 2012-12-05 |
| ATE338167T1 (en) | 2006-09-15 |
| EP1757731A2 (en) | 2007-02-28 |
| ES2271845T3 (en) | 2007-04-16 |
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