JPH0726355B2 - Process for the production of paper strips impregnated with synthetic resin in the form of solutions and dispersions - Google Patents

Abstract

A description is given of the soaking or impregnation of a paper web consisting mostly of cellulose fibres by a combination of dispersions and solutions of synthetic resins in a roll-type application unit installed in the papermaking machine, where the nature, degree of beating and dispersion particle size and the mixing ratio of dispersion and solution are matched to one another, for the manufacture of a fibre-containing sheet, in particular for covering parts of furniture.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing a paper strip impregnated with a synthetic resin.

BACKGROUND OF THE INVENTION The complete coating of plastic film casings for television and radio equipment, audio equipment and other furniture components with plastic films is conventional and well known. For that, especially PVC of different thickness
-A film is used.

This PVC-film is, for example, glued onto a wood chip board and subsequently from this composite material furniture elements or casings are manufactured in one working step according to the principles of the furniture industry. That is, a V-shaped groove is cut into this wood chip board, and the board is then folded or folded in this groove, thus producing the casing, furniture parts, etc. in one working step.

The key to this method is to make sure that the folds do not create creases in the film. The disadvantage of this method is again that the PVC film must be subjected to a corresponding surface treatment, for example a corona discharge treatment, directly before it is used in order to obtain good printability.

In addition, the wood chips must have a very clean and smooth surface (thin film application) in order to still be able to achieve economically acceptable results.

However, a particular disadvantage is that PVC is subject to temperature changes.
-The film exhibits extremely unfavorable dimensional stability (elongation / contraction behavior), low post-tear strength, slight light stability, and high electrostatic charging and softening at 75 ° C to 85 ° C. Is already happening. In addition, HCl-separation occurs when heating above 120 ° C.

It is known from the publication, for example from West German Patent No. 2550980, to impregnate a strip of base paper with an aqueous resin solution for immersion and / or an aqueous dispersion by absorption of the immersion liquid in the absorption zone. In which case at least a sufficient amount for complete saturation is applied on the surface of the paper strip and subsequently this paper strip is guided over the absorption zone in which the impregnating liquid is admixed with another solution. Absorb on the surface. However, dipping resin solutions are resins based on urea resins, melamine resins and phenol resins, which contain formaldehyde and give brittle products.

In the case of this method, the raw paper strip is fed to a second device after its production, it is unwound, impregnated using additional equipment such as an absorption zone and a drying device, and rewound. Needed to be taken.

Moreover, in the case of this method, the distribution of the impregnating liquid over the cross section of the paper is non-uniform, so that a strongly impregnating zone occurs with a slightly impregnating zone, which leads to the decomposition of the paper core. .

West German Patent Application Publication No. 3024394 describes a method for producing a plastic decorative board in a paper machine by providing a paper strip with impregnation in the dry part of the paper machine and performing the impregnation in a size press. Have been described. However, the wetting of the paper strip in the press with the impregnating liquid not shown in detail is only complete if this paper strip is already pre-impregnated, and therefore also in this case. Need a special device.

The problem to be solved by the invention: Therefore, the object of the present invention is not to have the disadvantages of the pure plastics used in the usual way, but also to show better flexibility and water resistance. , A film-like, synthetic resin-containing strip material, which has stability to solvents and which has internal strength and good dimensional stability under the action of moisture and temperature changes.

Furthermore, the strip material must be able to be produced in a cost-effective manner from advantageous raw materials with as few additional processing steps as possible, excluding the production of the glazed paper strip itself.

Moreover, it is necessary according to the invention for the base paper to be as completely wetted and as impregnated as possible, for example by selecting the applicator or impregnator and, for example, the crushed state and the degree of crushing, the absorption of the fibrous material, the impregnated mixture. Or only to determine the porosity and surface roughness for the properties of the coating mixture, i.e. the properties of the paper such as its surface tension, viscosity, charge state and solids content.

Means to solve the problem: By the way, according to the invention, this problem is 50:50 to 10:90.
High absorbency and strength cellulose mixtures consisting of eucalyptus-cellulose and pine sulphate-cellulose in different ratios were ground to a grind of up to 35 ° SR or 15-25 ° SR.
Various pulverizations were carried out until the pulverization degree of 0.2 μm was reached, and a paper strip was formed from this cellulose mixture, optionally in combination with a synthetic fiber material.
acrylic acid, acrylic ester having an average particle size of less than m,
An aqueous dispersion of an anionic copolymer based on acrylonitrile, vinyl acetate and / or styrene and an anionic aqueous solution of a copolymer based on maleic anhydride or maleic acid and styrene, acrylic acid and acrylic acid ester is added in an amount of 100 to 10 It is solved by applying an impregnating liquid consisting of a mixture containing in a ratio of 1: 1 at a pH value of 7.5 to 100 in a size press in the drying section of the paper machine. In particular, the pH value lies between 8 and 9.

According to the present invention, the paper-belt cellulose is 50:50 from eucalyptus-cellulose and pinewood sulfate-cellulose.
The ratio is from ~ 10: 90, especially from 30:70 to 15:85.

The fibrous material of the paper strip includes other chemicals such as wet and dry solidifying agents, precipitants (fixing agents), synthetic resin dispersions, surfactants, colorants and fillers that change the properties of the base paper. Auxiliaries can be added.

Fillers are white pigments such as TiO ₂ , white smelt, kaolin.

Formaldehyde-free wet-solidifying agent in the form of, for example, polyamidoamine-epichlorohydrin resin, in an amount of 1 to 5% by weight, based on the absolute dry fiber material, and 1 to 20%, for example, acrylic acid, on the absolute dry fiber material. The addition of synthetic resin dispersions based on ester or styrene-butadiene and the addition of surfactants to improve the wettability of the paper in an amount of <0.5% relative to absolutely dry fiber material is within the scope of the invention. It turned out to be particularly advantageous.

According to the invention, when using anionic copolymeric aqueous dispersions which can be composed, for example, on the basis of acrylic acid, acrylates, vinyl acetate and / or styrene, the dispersed particles are, in particular, less than 0.2 μm. The film hardness is low to moderate, and the low minimum film forming temperature is particularly 30 ° C. or lower.

The ratio of the copolymer of the dispersion to the copolymer of the solution is in particular 500: 1 to 1: 1 for the active substance, preferably 100: 1 to 10: 1, ie 500 parts dispersion for 1 part solution. Parts to 1 part solution to 10 parts dispersion.

Also within the scope of the present invention, dipping resin solutions based on other plastics, for example styrene-butadiene-copolymers, polyurethane dispersions or polyolefin dispersions and urea-formaldehyde or melamine-formaldehyde resin contents of the impregnating agent. Can also be added.

The brittle nature of the impregnated paper can be prevented by using the mixture according to the invention containing the dipping resin solution.

It is also possible to add other auxiliaries such as wetting agents, viscosity modifiers, anti-adhesion and penetration aids, pigments, dyes and defoamers to the impregnating agent mixture.

As wetting and penetrating agents, substances which modify the surface tension between the liquid and solid phases, such as surfactants and emulsifiers, are used.

According to the invention, the permeation of the impregnating liquid can be advantageously controlled by the combination of maleic acid-copolymer and the substances which modify the surface tension.

According to the invention, this impregnating agent is used in the form of a mixture consisting of a solution and a dispersion having a solids content of 5-60%,
In this case, the viscosity is 10-60s (4mm according to DIN-cup)
Between

The application of the impregnating mixture and the coating mixture onto the fiber fleece is carried out in a paper machine in a roll applicator (size press). This size press is part of a paper machine, in which the sizing agent is applied to one or the other or both sides of the paper strip, or impregnation is carried out in this size press. According to the invention, a fiber fleece with a dry content of 98-92% is fed through a size press, thus dipping both sides.

According to the invention, further surface coating of the fiber fleece on one or both sides after this first treatment step of impregnation comprises:
It can be carried out in the paper machine with the same or similarly structured copolymer mixture, in which case an intermediate drying must take place between the two individual processing steps.

Subsequent coating on one side of the dried strip results in a dense surface which gives good printability or Ruckker coatability or coatability. Furthermore,
Only when the surface is coated on one side can this surface coating be carried out using a knife applicator. Roll coating of the coated paper strip on one side can be prevented by additional coating on the back side.

The paint applied in this way can be, for example, starch or a concentrated aqueous solution of CMC. The impregnated, one-sided coated strip can be subjected to additional finishing in a calender, for example using known mechanical finishing equipment or in separate work steps, to achieve the desired printability and lacquer application of the still coated surface. Sex increases.

According to the pressure used in the production of the fleece and in the finishing of the dip-coated strips obtained in such a way, said film of different thickness and different coarse density,
In particular, relatively hard and rigid substrates, such as stable composites, are suitable as decorative protective coatings on furniture parts, such as casings for television and radio equipment or casings for audio equipment (casing casings). By using a fiber-containing film which can be produced economically advantageously, the above-mentioned drawbacks of using PVC-films or other plastic films are avoided.

The fiber-containing film obtained according to the invention, which has a high flexibility, a dimensional stability on temperature change and a good barrier to water and solvents, likewise comprises: For example, expensive abrasive paper substrates for wet polishing, print carriers and advertising carriers, decorative wall materials (for example, dimensionally stable tables with or without flame retardant pigments), adhesive tapes, For example, it is particularly suitable as a support paper for floor covering.

Examples: Next, the present invention will be described in detail with reference to Examples.

Example 1 According to the invention, a base paper of the following composition and conditions is obtained on a duplex paper machine as a two-layer paper: pine wood sulfate-cellulose 80%. Eucalyptus tree-cellulose 20%. Grinding degree 30 ° SR [Schopper-Ri
egler)]. Additives, commercial product (calculated against absolute dry cellulose): Takul 1%. Formaldehyde-free wet solidifying agent 3%. Wetting and dispersing agents 0.3%. The ratio of the base paper having a weight per unit area of 90 g / m ² 2
Both sides were impregnated in a size press with a 0: 1 dispersion and solution of the synthetic resin mixture according to the invention. Surprisingly with this synthetic resin mixture according to the invention, the strong impregnation effect, which is characterized in particular by the layer strength and the rigidity, taking into account the water absorption that occurs in this case, is due to the synergistic effect of the dispersions and solutions used. Certainly, these dispersions and solutions, when used alone, cannot achieve the similarly intended good paper properties at all.

The following example demonstrates this fact. The sizing solution is partly water and has an optimum viscosity (DIN-cap <6
It had to be adjusted to 0S.4mm).

Formulation for groupless machines: 1-Synthetic resin-dispersion alone (acrylic ester, acrylonitrile and styrene based anionic copolymer aqueous dispersion), solid content 50%, average particle size approx.
0.1μ, medium hardness, minimum film formation temperature <1 ℃.

2-Plastic dispersion diluted with water, solids content 25%.

3-Plastic solution diluted with water alone (anionic aqueous solution of a carboxyl group-containing copolymer based on maleic anhydride), solids content approx. 12%.

4-Plastic solution with formaldehyde-free wet solidifier diluted with water, solids content about 10%.

5-dispersion (according to example 1) with a formaldehyde-free wet solidifying agent and defoamer diluted to a solids content of about 25% with water, and a solution (according to example 3) A plastics mixture according to the invention consisting of:

The pure plastic dispersion (formulation 1) actually has the strongest reduction in water absorption due to its good film-forming properties, but its penetration into the base paper is poor. This is evidenced by the slightly improved values in terms of layer strength and stiffness.

By diluting this dispersion with water (formulation 2), a strong penetration into the raw paper takes place at the same time when the water uptake is increased and the elasticity of the impregnated paper is still insufficient.

Further, the insufficient impregnation is remarkable in that the carding strength of the paper surface is insufficient. Impregnating the base paper with a water-diluted synthetic resin solution (formulation 3) leads in fact to improved elasticity, but leads to significantly degraded layer strength.

Also, the addition of the wet setting agent (Formulation 4) does not cause any change in the essential properties of the impregnated paper.

The desired high size of the sizing fluid, characterized by a layer strength of about 10% higher than for formulation 2, a relatively low water absorption and a maximum elasticity (about 10% less rigid than for formulation 3). The impregnation effect, and thus all the intended good paper properties, are achieved only by the synthetic resin mixture according to the invention of the dispersions and solutions (formulation 5).

The unexpectedly high impregnating effect on the action of the individual components (dispersion, solution, wet solidifying agent) is attributed to the synergistic action of the dispersion and the solution.

Example 2 In another series of tests, a medium hardness synthetic resin dispersion (5) was replaced by a hard dispersion having a particle size of about 0.15μ at a minimum film forming temperature of about 25 ° C. The dispersion was an acrylic ester and styrene based copolymer aqueous dispersion.

The following properties of the base paper impregnated with this dispersion were obtained (restated for better understanding of the results obtained with the formulation 5 from the preceding first test): 6-Formaldehyde-free wet solidifying agent-diluted synthetic resin dispersion with water, solids content approx. 25%.

7-Synthetic resin mixture according to the invention consisting of a dispersion in the ratio 20: 1 and a solution according to Example 3 with the addition of formaldehyde-free wet solidifier and defoamer diluted to a solids content of about 25% with water. .

Using the pure synthetic resin dispersion according to formulation 6, formulation 1
In the cases of 2 and 2, the intended high impregnation effect cannot be achieved as already proved. Only the combination of the dispersion and the solution according to the invention leads to the desired paper properties, in which case the elasticity of the impregnated paper, due to the high film hardness of the selected dispersion, is more than that with the formulation 5. The result is bad.

Subsequent polishing of the paper impregnated according to the invention reduces the stiffness by about 10-20% and the water absorption by about 15-20%, while the layer strength remains almost unchanged. is there.

Example 3 In the immediately following test, dispersions and solutions were used to impregnate the base paper according to Example 1 in a ratio of 2: 1 with a synthetic resin mixture according to the invention in combination with a urea-formaldehyde resin.

Synthetic resin dispersion according to formulation 6 in combination with urea-formaldehyde resin in a ratio of 8-1: 2 alone.

A synthetic resin mixture according to the invention consisting of a dispersion and a solution according to formulation 7 (ratio 20: 1) in combination with a urea resin in the ratio 9-1: 2.

A synthetic resin dispersion having a solids content of 50%, an average particle size of about 0.15μ, a medium film hardness, and a minimum film formation temperature of 120 ° C. in a combination with a urea-formaldehyde resin in a ratio of 10-1: 2.
Alone (acrylate based anionic copolymer aqueous dispersion).

A synthetic resin mixture according to the invention consisting of a dispersion (according to formulation 10) and a solution (according to formulation 3) in the ratio 20: 1 in combination with a urea resin in the ratio 11-1: 2.

The resulting properties of the impregnated paper are listed in the following table: Also, synthetic resin dispersions and dipping resins such as urea-formaldehyde resins (for example, this is commonly used for impregnating decorative base papers in a separate impregnator).
In combination with lead to improved properties of the base paper. In this case, the type of synthetic resin dispersion used essentially determines the treatment liquid absorption, the porosity, the water absorption and the layer strength of the paper (see formulations 8 and 10).

However, this special dipping resin-synthetic resin-
In the case of the combination too, the desired high impregnation effect and thus the intended properties of the impregnated paper are obtained (see formulations 9 and 11). For that purpose, for example, the porosity and the water absorption are significantly reduced and the layer strength is increased. However, the level of layer strength is slightly lower than for Formulations 1 and 2 due to the relatively high dipping resin content.

Claims (8)

[Claims] 1. A method for producing a paper band impregnated with a synthetic resin, which is a mixture of eucalyptus-cellulose and pine sulphate-cellulose having a ratio of 50:50 to 10:90 and having a high absorption and strength. Is crushed to a maximum crushing degree of 35 ° SR or variously crushed to a crushing degree of 15 to 25 ° SR, and a paper strip is formed from this cellulose mixture. Anionic copolymer aqueous dispersions based on acrylic acid, acrylic acid esters, acrylonitrile, vinyl acetate and / or styrene with an average particle size of less than 0.2 μm, maleic anhydride or maleic acid and styrene, acrylic acid and acrylic acid An impregnating solution consisting of a mixture containing an anionic aqueous solution of an ester-based copolymer in a ratio of 100 to 10: 1 was dried on a paper machine at a pH value of 7.5 to 100. A method for producing a paper strip impregnated with a synthetic resin, characterized by applying in a size press in a drying section. 2. The method according to claim 1, wherein the pH value is adjusted to the range of 8-9. 3. A method according to claim 1 or 2 in which other chemical auxiliaries are added to the fibrous material of the paper band. 4. The ratio of the anionic copolymer aqueous dispersion having a slight to moderate film hardness and the minimum film forming temperature of 30 ° C. or less to the anionic solution of the copolymer is adjusted to 25 to 15: 1, and Use auxiliaries and pigments and colorants,
The method according to any one of claims 1 to 3. 5. A process according to claim 1, wherein the mixture of dispersion and solution additionally contains a content of surfactant. 6. The surfactant according to any one of claims 1 to 5, wherein the content of the surfactant is 0.05 to 1.5% with respect to the mixture of the dispersion and the solution. Method. 7. Infiltration of the fiber fleece in a paper strip is carried out by roll coating on both sides in the first treatment step in the paper machine and coating is carried out by knife coating on one side in the second treatment step. , This knife application is connected to the surface polishing of the paper strip, Claim 1
Item 7. The method according to any one of Items 6 to 6. 8. A surface post-treatment on one side after drying and surface-polishing a paper strip, claim 1.
The method according to any one of items 1 to 7.