FI120369B - Paper impregnated with resin - Google Patents

Description

PAPER WITH IMPREGNATED SHARES

State of the art

The invention relates to paper used in the manufacture of a laminate (or coated sheet). This paper can be used in a so-called. in the manufacture of impregnate. Such an impregnate is used as a coating material and in the manufacture of laminates (including compact laminates).

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During impregnation, the paper is impregnated with a solvent-mixed (solvent or aqueous) pre-condensed resin, resin or latex dispersion, later referred to as the resin. After absorption, the solvent is removed. The intermediate thus obtained is called impregnate. When the resin is cured, a strong sheet-like laminate or coating is obtained. The paper gives the structure mechanical strength. The cured resin, on the other hand, provides rigidity and features lacking on paper alone, such as resistance to water and various chemicals. Typically, condensation resins such as phenolic resin, melamine resin, urea formaldehyde resin, or a mixture thereof are used for impregnation. In addition, various amino, polyester or biopolymer-based resins (either as such or as additives) may be used for impregnation. The composition to be absorbed may be a solution or dispersion. Usually, the impregnates are formed into a laminate by compressing together a plurality of impregnates by means of heat and pressure, whereby the curing reaction occurs simultaneously. Impregnate can also be used as such for coating, for example, one or more sheets are often laminated or glued to the surface of a wooden board.

The interaction between paper and resin is a key factor in laminate formation. This affects both the impregnability (runnability of the impregnation machine), the compression of the laminate (hardening of the resin, the movement of the resin and its filling in the compression) and the properties of the pressed laminate.

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In the paper, fillers can be used to lower the price and improve the properties of the laminate, for example, the thermoplastic properties (especially the so-called post-forming properties). However, conventional fillers (such as talc, kaolin) may impair certain properties of the laminate, such as impact strength, water absorbance (cooking test) and heat resistance.

Critical properties of paper include impregnation rate (absorption in length, cross (x, y) and depth (z)) and drying (drying energy required). The amount of penetrable resin and the rate of absorption are influenced by the moisture, porosity, 10 pore size distribution, temperature and surface chemistry of the paper. In addition, it is affected by the resin mixture solvent, solids content, viscosity, surface tension, degree of cure, and temperature.

Poor absorption of the resin mixture causes problems. The 15 air remaining in the pores of the impregnate causes appearance defects. Furthermore, unless the resin is absorbed uniformly in the z-direction, the cross-section of the compressed laminate does not appear to be uniform, and in the worst case, this region may, at a weaker point, cause the structure to disintegrate in the z direction.

Poor absorption of the resin into the paper is typically improved by diluting the mixture with water, methanol, or a mixture thereof. As a result of dilution, the required drying energy is increased. The solvent used may also cause other undesirable side effects.

In order to obtain a uniform resin distribution, it is required that the resin be able to move * during compression. This mobility during compression is described in the so-called. 'flow value. It can be measured in the impregnate. <

Various fillers can be expected to improve the deformability of the paper even before 30 impregnations. Small amounts of filler can have positive effects, for example, in board food applications.

3 Fillers have been used in laminates to improve postformability. Postfor-Ming properties refer to post-ductility (such as bendability) under heating and mechanical bending. The postforming properties of a laminate can be measured by bending the laminate at different temperatures at different speeds.

The laminate must withstand mechanical stress. Mechanical resistance is assessed, inter alia, by various impact tests. Filler in impregnable papers generally reduces the impact resistance of the laminate.

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Hard fillers have a significant effect on the workability of the laminate (sawing, milling, drilling).

Good heat resistance of laminate is especially required for 15-layer laminates used in kitchen furniture. Typically, the use of fillers in impregnable paper also reduces the heat resistance of the laminate.

The state of the art is illustrated, for example, in A. Gardziella, L.A. Pilata, A. Knop, Phenolic Resins, 2nd ed., Springer-Veiiag, 2000.

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General description of the invention

A paper according to independent claim 1 has now been invented. Other preferred embodiments of the invention are disclosed in the other claims.

The paper according to the invention contains a curable resin and gypsum.

Surprisingly, it has been found that the use of gypsum offers certain advantages, particularly in the manufacture and properties of impregnates and laminates. In particular, gypsum appears to promote the uniform distribution of the resin in the impregnate and to improve flow in compression. Above all, the amount of air bubbles in the laminate is reduced and the relationship between resin and fibers throughout the laminate is leveled.

Detailed Description of the Invention

The paper used in the production of the laminate according to the invention contains gypsum, for example, from 0.1 to 45%, preferably from 0.5 to 15%, by weight of non-impregnated dry paper.

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The resin may in particular be a condensation resin. In particular, the resin may be a resin curable by condensation reaction. Such resins include, for example, phenolic resin, melamine resin, urea-formaldehyde resin, or a mixture thereof. In addition, various amino-, polyester- or biopolymer-based resins 15 (either as such or as additives) may be used in the impregnation.

The resin may also be a thermoplastic latex or resin mixture.

The amount of resin may be, for example, 10-80%, preferably 20-60%, by weight of the impregnate 20 dry weight.

The impregnable base paper according to the invention can be made by impregnating and pressing various products. These include, for example, roll laminates, post-forming laminates, planar laminates, compact laminates, coating films 25 (such as direct compression films), adhesive films, and various moldings.

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According to the invention, the use of gypsum in base paper has a surprisingly positive effect on impregnation, compression of the laminate and properties of the laminate. In particular, the ductility properties are improved. This way, J can also be better prepared

various shapes directly by squeezing the impregnate (cups, molds, etc. muo-5 top moldings) or otherwise shaping.

Gypsum has not been used extensively as a filler for paper, mainly due to its high porosity in water (about 2 g / l). However, in recent years, the use of gypsum for paper coating of paper has increased. Gypsum has not been used at all as a raw material for laminate-10 papers.

According to the invention, gypsum may be added to the paper structure during its manufacture or at the wet end of the paper machine, during the forming of the web with the paper machine or press portion, or in finishing such as surface sizing or coating. The coating may be carried out, for example, by spray or blade coating. The dosing in the web can be assisted, for example, by vacuum. Gypsum can also be added to the fiber structure by doping the gypsum onto the fiber surface, for example by so-called gypsum. fiber loading in an aqueous fiber suspension; or doping with a soluble gypsum or gypsum suspension in a paper web. The gypsum can also be added in the im-20 impregnation step mixed with the resin. Gypsum can also be added after impregnation (PPA).

It is surprising that gypsum can be used in impregnation base paper. Namely, it has been assumed that too much gypsum is soluble in the impregnable composition (e.g., the problem of buying and curing sa-25 on the resin) and that during the laminate compression, the crystal-water cleavage of the gypsum causes the compression to bubble.

Compared to gypsum-based resin impregnated base paper with conventional papers, the following benefits can be achieved in the impregnation process: -exposed swelling in impregnation.

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Due to the improved z-distribution of the resin, it is not necessary to dilute the impregnation resin excessively, whereby other beneficial effects can be achieved. These include the reduced need for drying energy, for example increasing the running speed.

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The gypsum-containing resin impregnated base paper can achieve the following advantages for the pressing process and the laminate (coating): - improved appearance (without being bound by any theory, it is assumed that the use of gypsum can improve appearance due to smoother resin distribution and improved water flow). usability of films in the building and transport industry - greater laminate thickness is achieved compared to other filler-containing papers (without being bound to any theory, gypsum is expected to affect laminate density due to its relatively low density) - substantially improved bending speed and improved bending properties reduced water absorption in the cooking test (without being bound by theory, it is assumed that the improved cooking test result is due to Improved heat resistance (without being bound to any theory, it is assumed that the heat resistance is improved due to the favorable fiber-resin interaction) fiber system) - the price of the end product, especially in special applications, decreases due to reduced need for fiber material and increased production speed.

Without being bound by any theory, it is believed that much of the improved properties of the laminate are associated with more favorable resin distribution in the impregnate and improved resin mobility in compression. Particularly as the air-10 bubbles in the laminate shrink and shrink, better appearance and better properties are achieved in various stress tests (cooking test, heat resistance, thermoplasticity).

Without being bound by any theory, it is assumed that the water content of the gypsum improves the properties of the laminate in various heating-related stresses (heat resistance, thermoplasticity, post-ductility, fire resistance).

Without being bound by any theory, it is also assumed that gypsum has a more positive effect on the condensation properties of the resin than other fillers.

Typical paper properties for impregnated paper include high purity, high porosity, sufficient absorbency, a uniform thickness and density profile, defined and uniform basis weight, including small scale basis weight, defined and reproducible strength ratio, sufficient wet strength. Typically, kraft paper made from unbleached pulp is used. For example, the paper may have a basis weight of 20 to 350 g / m2.

EXAMPLES 30 In the examples, paper-free filler, talc or gypsum-containing paper was used, the fiber raw material being brown unbleached coniferous pulp. Talc and gypsum were added to the mass. The paper was impregnated with phenolic resins so that, depending on the product, the amount of dry resin in the impregnate was between 20 and 60%.

Impregnation with phenol resin was carried out on a pilot impregnation machine and the laminates were pressed with a laboratory press. Impregnation was performed with both standard resin and post-forming resins.

In addition, impregnation was carried out on a production scale with CPL (continuous pressure laminate) resin. The production-scale compression of these impregnates was accomplished by 10 continuous laminating processes.

Table 1. Main quality characteristics of the papers tested.

Test point Filler-free Gypsum-containing paper Talc-containing

Gross weight (ISO 536) 155 g / m2 150 g / m2 150 g / m2

Equilibrium Humidity (ISO 2878-m 7.8% 6.3% 6.6%

Density (ISO 534) 727 kg / m3 684 kg / m3 730 kg / m3

Gurley (SCAN P-19) 14.8 s 9.3 s 13 £ s

Clamp (IOmin) 51mm 45mm 43mm

Boat test (with water) <1 sec <1 sec 1.2 sec

Boat test (phenolic resin) 22 s 11 s 14 s

Resin Ability (Phenolic Resin) 136% 137% 125%

Tensile strength index (SCAN P-67) 40.1 Nm / g 27.9 Nm / g 27.2 Nm / g

Tensile strength when wet SCAN P-67 920 N / m 715 N / m 703 N / m

Ash (ISO 1762 but 550 ° C 1.91% 16.0% 23.7% "pH ~ 8 ^ 2Ϊ 7 ^ 04 8 ^ 66 Electrical conductivity 2.57 mS / m 119.8 mS / m 3.13 mS / m 15 9

Example 1. Impregnation with standard resin

Table 2 shows the results of the impregnation test with standard resin. The resin used was a typical phenolic resin used in flat and compact laminates.

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Table 2. Results of the impregnation test with standard resin

Test point Standard quality Gypsum Talc as filler as filler filler

Travel speed 4.4 m / min 4.4 m / min 4.4 m / min

Drying temperature 170/170 ° C 170/170 ° C 170/170 ° C

Drying air pressure (drying air 20 / 20kPa 17 / 17kPa 17/17 kPa

Resin 28.8% 29.7% ~ 29.2%

Volatile 7.1% 7.5% 7 $%

Flow 0.0% 0.3% Ö, 0% ~ pH 8 / Ϊ3 TM 8 / ΓΪ Conductivity 4.90 mS / m 140.1 mS / m 5.54 mS / m

The gypsum-containing paper achieved a slightly better flow rate of the resin than the other fire classes.

Laminates with standard resin 15 Table 3 shows the results of laminates pressed from standard resin impregnated papers.

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Table 3. Properties of standard resin laminate

Test Point Standard Quality Gypsum Talc

Laminate insert / structure (4 frames + decoi (4 frames + decoi (4 frames + decoi)

Laminate compression (90 bar / 140 ° C / 10 mi (90 bar / 140 ° C / 10 mi) (90 bar / 140 ° C / 10 mi DIN cooking test, 2 h - weight change 8.6% 7.1% 6 , 9% - Change in thickness 13.5% 10.4% 9.1%

Heat resistance 170-180 170 ° C 160 ° C

Gypsum-containing paper achieved better cooking test results than filler-free 5 stick paper. In addition, gypsum-containing paper achieved better heat resistance than talc-containing paper.

Example 2. Impregnation with Postforming Resin 10

Table 4 shows the results of the impregnation test with postforming resin. The resin used was a typical plasticizer-containing phenolic resin.

Table 4. Postforming resin impregnation test results 15

Test Point Standard Quality Gypsum Talc

Travel speed 4.4 m / min 4.4 m / min 4.4 m / min

Drying temperature 170/170 ° C 170/170 ° C 170/170 ° C

Blowing 18/18 kPa 18/18 kPa 18/18 kPa

Resin 31.5% 31.9% 31.3%

Volatile 8.5% 8.9% 8.7%

Flow 0.6% 1.0% 0.8% ”pH 8 ^ 01 Ί, 85 8 ^ 01 11

The gypsum-containing paper achieved a slightly better flow value than the other test points.

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Laminates from postforming resin impregnated papers

Table 5 shows the results of laminates pressed on postforming resin impregnated papers.

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Table 5. Properties of the postforming resin laminate

Test point Standard quality Gypsum-containing Talc

Laminate compression

Thickness (3 frames + decor) 0.569 mm 0.541 mm 0.532 mm

Thickness (4 stems) 0.668 mm 0.624 mm 0.617 mm

Density (3 frames + decor) kg / m3 1.41 1.46 1.49

Density (4 frames) kg / m3 1.33 1.38 1.41 DIN cooking test, 2 h (3 frames + dec) - Weight change 7.9% 6.6% 6.9% - Change in thickness 12.6 % 11.5% 11.9%

Melting point / bubbling point 31 sec / 33 sec 30 sec / 29 sec 29 sec / 11 sec

Postforming bend, 90 ° 57 s 20 s 15

Postforming bend, 100 ° 105 s 36 s 23

Heat resistance 200 ° C 200 ° C 170-180 ° C

Post-ductility is better on gypsum-containing paper than non-filler paper.

15 The bubble point and heat resistance on gypsum-containing paper were similar to standard paper.

Gypsum-containing paper achieved a better cooking test result than standard paper.

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Figure 1 further shows the z-penetration of the resin into the paper.

Example 3. Impregnation with CPL Resin

Table 6 shows the results of the impregnation test with CPL resin. The resin was a typical mixture of melamine and phenolic resin used in the CPL process.

10 Table 6. Impregnation Results with CPL Resin

Test Point Standard Gypsum Talc

Travel speed 38 m / min 38 m / min 38 m / min

Nipple clearance (pm) 618,561,585 ”Resin 38.4% 41.1% 40.6%

Volatile 7.3% 6.9% 7.1%

Flow '0.50% 0.14% 0.59% "pH ___ __ __ CPL Minimum Bubble Time (160C 50 Bar) 14 8 30

The resin absorbency on gypsum-containing paper was the best that had to be compensated by 15 nip clearances. Plaster also had the best CPL minimum bubble time.

Preparation and Properties of CPL Laminates The 20 CPL impregnates were run with laminates using a CPL press. The variable was the running speed, for which a maximum was sought, where bubbles had not yet formed in the laminate. The results are shown in Table 7.

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Table 7. CPL compression and laminate results

Test Point Standard Quality Gypsum Talc

Travel speed 10m / min 15m / min 14m / min

Running speed 11 m / min - Maximum machine speed (small bubbles) was 15 m / min

Thickness (3 frames + decor) 0.728 mm 0.692 mm 0.693 mm DIN cooking test, 2 h (3 frames + decc weight change 17.0% 10.0% 14.5% - thickness change 26.4% 18.0% 31 9%

Note Bubbles in the soup No bubbles in the soup Bubbles in the soup 5 Gypsum-containing paper was by far the best in the cooking test. In addition, the maximum running speed achieved in the CPL process was highest on this paper.

Both filler points achieved higher running speeds than the standard quality. No limit speed was found for gypsum, as the product was still operating at the highest available 10 speeds (15 m / min). The gypsum-containing test point was the only one that passed the 2 h cooking test without bubbles.

The results are consistent with minimum bubble time measurements, which reinforce the notion of the utility of higher compression speeds.

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Table 8. Results of CPL laminates

Test Point Standard Quality Gypsum Talc

Melting Point / Bubble Point Does not withstand heat for 30s / 6s 31s / 4s

Postforming bend, 90 0 37 s 16 s 22 s

Postforming bend, 100 0 103 s 28 s 38 s

Heat resistance 160 ° C 180-190 ° C 180 ° C

5 Gypsum-containing paper achieved best heat resistance and best postforming properties.

Figure 2 further shows the z-penetration of the resin in the paper.

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Summary of results

The suitability of gypsum as a raw material for impregnation was investigated in standard phenolic resin laminate and postforming laminate as well as in the CPL product. The comparison was made on full-15 paper-free and talc-containing paper.

In the CPL product (especially postforming) gypsum paper proved to be completely superior to the other paper grades studied. No bubbling occurred within the speed range available with the CPL press at the time of laminate production. The production rate was the highest and, in addition, it was the only product which passed the 2 h cooking test without bubbling.

Postforming phenolic resin laminate exhibited significantly better post-ductility properties than non-filler paper.

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Claims (6)

1. Paper, characterized in that the paper contains gypsum in which impregnable resin is impregnated. 5 Paper according to claim 1, which contains gypsum 0.1 to 45%, preferably 0.5 to 15% of the dry weight of the paper. Paper according to claim 1 or 2, in which resin is absorbed 10-80%, preferably 20-60% of the dry weight of the impregnate to form an impregnate. Paper according to any one of claims 1-3, wherein the absorbed resin contains phenolic resin, melamine resin, urea formaldehyde resin or amino-, polyester- or biopolymer-based resin. 15 5. Use of paper impregnated with resin containing plaster in the manufacture of a laminate. Use according to claim 5 for improving the forming properties of a laminate to be made of paper, in particular the post forming properties, for improving the appearance, for reducing water permeability, for improving heat uniformity or for improving printing speed. 25