JP5208037B2 - Method for producing overlay base paper - Google Patents

Description

The present invention is mainly used in the thermosetting resin decorative plate, a method of manufacturing Oh overlays the base paper.

A thermosetting resin decorative board represented by a melamine decorative board is provided with an overlay layer for the purpose of protecting the printed pattern of the pattern layer (decorative layer), imparting abrasion resistance, chemical resistance, etc., and further for design purposes. . The overlay layer is the outermost layer of the decorative board, and should not interfere with the color pattern of the pattern layer as the main design layer, and requires high transparency. This is the same even when a design material is included in the overlay layer, and high design properties are exhibited by making the portion other than the design material transparent. The overlay layer is generally composed of an overlay paper coated with a thermosetting resin, and natural pulp fibers that are highly digested and bleached with less coloring impurities are used for the overlay base paper. Moreover, the beating of the pulp fiber can be suppressed lightly so as not to impede the permeability of the resin when coating the thermosetting resin. Of course, the lower the basis weight of the base paper, the better the transparency when it is formed into a molded plate, and the one with 18 to 50 g / m ² is common.

On the other hand, the overlay base paper is required to have sufficient wet tensile strength that does not cause paper breakage when it is coated with an aqueous solution or water-dispersed resin such as melamine formaldehyde resin. As a method for imparting wet tensile strength to paper, a method of internally adding a wet paper strength agent of melamine formaldehyde type, urea formaldehyde type or polyamide polyamine epichlorohydrin type is common. In recent years, melamine formaldehyde type and urea formaldehyde type wet paper strength agents have been switched to polyamide polyamine epichlorohydrin type wet paper strength agents because free formaldehyde is generated and the working environment is deteriorated. Yes.
The use of polyamide polyamine epichlorohydrin-based wet paper strength agent is increasing also in the overlay base paper. However, when the paper strength agent is thermally cured, the paper is discolored or coated with a thermosetting resin. There is a problem that the overlay layer becomes cloudy when the resin is inhibited from penetrating into the pulp to form a molded plate. Accordingly, the addition amount is limited to 2.0 parts by weight or less with respect to 100 parts by weight of the pulp fiber, and the strength characteristics of the pulp fiber itself are greatly reflected in the wet tensile strength.

However, as mentioned above, natural pulp fibers that have been highly digested and bleached are used for the overlay base paper, but the pulp fibers have few components that contribute to strength properties such as hemicellulose and lignin, and provide sufficient wet tensile strength. It's hard to be done. In addition, characteristics such as mild beating and low basis weight are factors that make it difficult to obtain wet tensile strength.

As a method for achieving both transparency and strength properties of paper, a method of making non-wood fiber soft cells (Patent Document 1), a method of mixing bacterial cellulose (Patent Document 2), and a method of mixing fine fiberized pulp (Patent Document 2) Patent Document 3), a method of blending fibrous starch (Patent Document 4) is known, but in any case, the paper itself becomes dense and obstructs the penetration of the thermosetting resin. In this case, sufficient transparency cannot be obtained.
Also, a method of internally adding viscous cationized modified starch granules (Patent Document 5), a method of colloidizing the pulp surface with a strong acid such as sulfuric acid or phosphoric acid, or a base such as zinc chloride or lithium thiocyanate ( Patent Document 6) has been proposed, but in these methods, the gaps between the pulp fibers themselves disappear and the thermosetting resin cannot penetrate.
In addition, there is also known a method (Patent Document 7) in which polyolefin synthetic pulp is mixed and welded and then impregnated with a clarifying agent (Patent Document 7), but when impregnated and hot-pressed using a thermosetting resin as a clarifying agent The polyolefin synthetic fiber and the thermosetting resin are separated and are not transparent.

JP 2008-75199 A JP H9-195193A Japanese Patent Laid-Open No. H8-188980 Japanese Patent Laid-Open No. H6-192992 Japanese Patent Laid-Open No. H4-209897 Japanese Patent Publication No. S36-1702 JP S50-35409 A

This invention makes it a subject to provide the manufacturing method of the overlay base paper which can reduce the trouble of white turbidity at the time of setting it as the shaping | molding board by using a polyamide polyamine epichlorohydrin type wet paper strength agent .

As a result of research to solve such problems, the inventors have found that the degree of polymerization of natural pulp fibers and the α cellulose content of the pulp fibers affect the wet tensile strength of the overlay base paper and the transparency when used as a molded board. To solve the above-mentioned problems.

That is, the present invention
(1) A natural pulp fiber having a degree of polymerization of 860 or more and an α-cellulose content of 85 to 92% by weight is adjusted to a Canadian standard freeness of 550 to 800 ml, and 100 parts by weight of the natural pulp fiber, A method for producing an overlay base paper, comprising wet-making a pulp slurry to which 0.3 to 2.0 parts by weight of a polyamide polyamine epichlorohydrin wet paper strength agent is added.

According to the present invention, when wet-making an overlay base paper using a polyamide polyamine epichlorohydrin-based wet paper strength agent, a specific natural pulp fiber excellent in wet tensile strength and transparency when used as a molded board is used. By doing so, the amount of wet paper strength agent used can be reduced, so it is possible to reduce the trouble of white turbidity when used as a molded plate, and due to the transparency when using natural pulp molded plate and the effect of reducing wet paper strength agent, An overlay base paper excellent in transparency when formed into a molded plate can be obtained .

Hereinafter, the present invention will be specifically described.
The natural pulp fiber used in the present invention has a polymerization degree of 860 or more and an α cellulose content of 85 to 92% by weight. For pulp fibers having a polymerization degree of less than 860, transparency when formed into a molded plate is lowered. Moreover, even if it is a pulp fiber with a polymerization degree of 860 or more, when the α cellulose content is higher than 92% by weight, the wet tensile strength is lowered. Also, pulp fibers having an α-cellulose content lower than 85% by weight can obtain wet tensile strength, but there is coloring due to residual lignin and the like, and transparency when formed into a molded plate is lowered.

The type of natural pulp fiber is not particularly limited, but wood pulp fiber that is highly digested and bleached with few impurities and foreign substances that impair transparency when formed into a molded board is desirable. For example, softwood bleached kraft pulp (NBKP) ), Hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP), hardwood bleached sulfite pulp (LBSP) conifer dissolved kraft pulp (NDKP), hardwood melted kraft pulp (LDKP), conifer dissolved sulfite pulp (NDSP) ), Hardwood dissolved sulfite pulp (LDSP) and the like. By using these alone or in combination, a natural fiber pulp having a polymerization degree of 860 or more and an α-cellulose content of 85 to 92% by weight can be obtained. In addition, a polymerization degree and alpha cellulose content rate are based on the measuring method of an Example. The beating degree is desirably a Canadian standard freeness of 550 to 800 ml. If the beating degree is made smaller than the Canadian standard freeness of 550 ml, the paper becomes dense and impedes the penetration of the thermosetting resin. Transparency cannot be obtained.

The polyamide polyamine epichlorohydrin wet strength agent used in the present invention is generally produced by reacting epichlorohydrin with a polyamide polyamine resin obtained by reacting dicarboxylic acid, adipic acid or diethylenetriamine. It contains low molecular weight organic halogen compounds such as epichlorohydrin, 1,3-dichloropropanol, 3-chloro-1,2-propanediol, which are pointed to be mutagenic as products. In recent years, paper manufacturers have been making efforts to reduce various low-molecular-weight organic halogen compounds, and recently, products having a low-molecular-weight halogen compound of less than 1% by weight are commercially available. Also in the present invention, it is desirable to use a polyamide polyamine epichlorohydrin wet paper strength agent having a low content of low-molecular organic halogen compounds.

As a method for coating a resin with paper in the production of a thermosetting resin decorative board, the most commonly used method is impregnation by dipping. In the dipping impregnation method, the overlay base paper is required to have a wet tensile strength of at least 0.15 kg / 15 mm or more. Therefore, it is preferable to add 0.3 to 2.0 parts by weight with respect to the pulp as the addition amount of the polyamide polyamine epichlorohydrin wet paper strength agent. If the amount is less than 0.3 parts by weight, sufficient wet tensile strength cannot be obtained. Transparency at the time of being reduced. It is also undesirable from a cost standpoint.

In the present invention, various papermaking chemicals such as a paper strength aid, a pH adjuster, a viscosity agent, and an antifoaming agent can be added as necessary. Examples of paper strength aids include carboxymethylcellulose, hydroxyethylcellulose, cation-modified starch, oxidized starch, vegetable gum, polyvinyl alcohol, polyacrylamide, and polyvinylamine. From the viewpoint of transparency when used as a molded plate, carboxymethylcellulose is used. desirable. As the pH adjuster, sodium aluminate, sodium hydroxide, sodium phosphate, aluminum sulfate, citric acid and the like are used. Examples of the sticking agent include polyethylene oxide, sodium polyacrylate, polyphosphate, and the like, but polyethylene oxide is desirable for obtaining a good texture. Examples of the antifoaming agent include fatty acid ester type, higher alcohol type, and silicone type, and any of them may be used.

Furthermore, in order to give abrasion resistance to the decorative board surface, an abrasive can be mixed as needed. Examples of the type of abrasive include aluminum oxide, silica, silicon carbide, tungsten carbide, glass fiber, fine glass, ceramic fiber, asbestos and the like.

In addition, for the purpose of design, a design material can be mixed as needed. There are no particular limitations on the type of design material, but high-gloss particles with a metal coating on the surface of glass flakes and mica pieces, synthetic fibers such as rayon, polyester, and nylon, and non-wood fibers such as hemp, bamboo, and straw Can be mentioned.

As the paper making method of the overlay base paper, a long net, a round net, an inclined wire, or a multi-layer paper machine is used, but any method may be used.

It is desirable to make the paper so that the basis weight of the obtained base paper is 15 to 60 g / m ² . When the basis weight is lower than 15 g / m ² , the wet tensile strength of the base paper is weak and the paper is cut when the resin is coated. On the other hand, when the basis weight is higher than 60 g / m ² , the transparency when formed into a molded plate is lowered.

A highly transparent overlay can be obtained by coating the overlay base paper of the present invention with a thermosetting resin. The resin may be anything as long as it can be generally used for coating, but melamine formaldehyde resin is desirable in terms of transparency and strength.
The optimum amount of the coating resin varies depending on the molding method and the type of resin, but if it is a normal molding method, it is preferably 150 to 350% by weight with respect to the base paper. Further, in the dry laminate manufacturing method in which the resin is not coated on the pattern paper (decorative paper), but only the overlay base paper is coated with the resin and hot pressing is performed, the amount of the impregnated resin is desirably 350 to 600% by weight. Examples of the resin coating method include an impregnation method and a coating method, and any method may be used.

Next, the present invention will be described more specifically with reference to examples. In addition, evaluation in a present Example and a comparative example was performed with the following method.

<Evaluation method>
(1) Degree of polymerization Measured according to the copper ethylenediamine viscosity method of JIS P8215. From the intrinsic viscosity [η] obtained by the measurement, the degree of polymerization DP was determined from the following calculation formula in accordance with Staudinger's viscosity law.
DP = [η] /5.7×10 ⁻³

(2) α cellulose content The measurement was performed according to JIS P8101.

<Evaluation method>
(3) Wet tensile strength Measurement was performed according to the general method of JIS P8135.

(4) Transparency For the black back molded plate produced by the method described later, a spectrophotometer (manufactured by Macbeth Co., MS-2020) is used, and a molded plate without overlay as a standard, L * with the molded plate with overlay The color difference (Delta E) of the a * b * color system was measured and used as an index of transparency. As the numerical value is smaller, the transparency is better. As a guideline for evaluation, if there is a difference of 0.3 or more, it is possible to visually judge superiority.
-An overlay paper impregnated with melamine formaldehyde resin in an amount of 195 to 215% by weight with respect to the base paper was used as a black back molded plate sample. As pattern paper (decorative paper), three sheets of black decorative board base paper having a basis weight of 80 g / m ² impregnated with 90 to 110% by weight of melamine formaldehyde resin with respect to the base paper were used. Overlay paper and patterned paper are laminated on a phenolic core (Ota core) impregnated with phenolic resin, temperature 130-140 ° C, pressure 60-80 kg / cm ² , heating time 15 minutes, cooling time 7 minutes. Molded to produce a black back molded plate. A molded plate without overlay used as a colorimetric standard was formed by laminating only pattern paper and a phenol core, and molding was performed under the above conditions.

Example 1
As the pulp fiber, intercontinental (NBKP, manufactured by Canford) was used without being beaten (Canada standard freeness 715 ml), and WS as a polyamide polyamine epichlorohydrin wet paper strength agent with respect to 100 parts by weight of the pulp fiber. -4052 (manufactured by Starlight PMC) was added by 0.8 part, 0.27 part by weight of carboxymethylcellulose was added as a paper strength aid, and a basis weight of 23 g using a semi-automatic square paper machine (manufactured by Kumagai Riiki). An overlay base paper of / m ² was obtained.

(Example 2)
In Example 1, an overlay base paper was obtained in the same manner as in Example 1 except that the pulp fiber was replaced with Tarascon 92 (NBKP, manufactured by Tenbeck Co., Ltd.) and was used without being beaten (Canadian standard freeness 749 ml). .

(Example 3)
In Example 1, except that the pulp fiber was replaced with Alabama Pine (NBKP, manufactured by Alabama Pine Pulp Co., Ltd.) and was used as it was without beating (Canadian standard freeness 747 ml), an overlay base paper was prepared. Obtained.

(Comparative Example 1)
An overlay base paper was obtained in the same manner as in Example 1 except that the pulp fiber was replaced with Superplast VS (NBSP, manufactured by Volgaard) and used without being beaten (Canadian standard freeness 742 ml). It was.

(Comparative Example 2)
In Example 1, an overlay base paper was obtained in the same manner as in Example 1 except that the pulp fiber was replaced with Santa Fe (LBKP, manufactured by CMPC) and used without being beaten (Canadian standard freeness 662 ml).

(Comparative Example 3)
In Example 1, an overlay base paper was obtained in the same manner as in Example 1 except that the pulp fiber was replaced with Porosania (NDSP, manufactured by Leonia) and used without being beaten (Canada standard freeness 786 ml).

For Examples 1 to 3 and Comparative Examples 1 to 3, Table 1 shows the evaluation results of the degree of polymerization of the pulp fiber, the α cellulose content of the pulp fiber, the wet tensile strength of the base paper, and the molded plate. Shown in

As shown in Table 1, the overlay base paper produced in Examples 1 to 3 was superior to the overlay base paper produced in Comparative Examples 1 and 2 in terms of transparency when used as a molded plate. Further, the overlay base paper produced in Comparative Example 3 was inferior in wet tensile strength, although the transparency when formed into a molded plate was equal to or higher than the overlay base paper produced in Examples 1 to 3. From the above results, the overlay base paper produced in Examples 1 to 3 was excellent in wet tensile strength and excellent in transparency when formed into a molded plate.

Example 4
As a pulp fiber, Hinton (NBKP, manufactured by Westflare) was gently beaten to a Canadian standard freeness of 740 ml, and WS as a polyamide polyamine epichlorohydrin wet paper strength agent with respect to 100 parts by weight of the pulp fiber. -4052 (manufactured by Starlight PMC) 0.7 parts by weight, 0.24 parts by weight of carboxymethyl cellulose as a paper strength aid were added, and a basis weight of 34 g using a semi-automatic square paper machine (manufactured by Kumagai Riki). An overlay base paper of / m ² was obtained.

(Comparative Example 4)
In Example 4, the overlay fiber was used in the same manner as in Example 4 except that the pulp fiber was replaced with Superplast VS (NBSP, manufactured by Volgaard) and was used by gently beating it to a Canadian standard freeness of 730 ml. Got.

Table 2 shows the evaluation results of the degree of polymerization of the pulp fiber, the α cellulose content of the pulp fiber, the wet tensile strength of the base paper, and the transparency of the molded plate for Example 4 and Comparative Example 4 described above.

As shown in Table 2, the overlay base paper produced in Example 4 was superior to the overlay base paper produced in Comparative Example 4 in terms of transparency when formed into a molded plate, and was excellent in wet tensile strength.

As described above, according to the present invention, trouble of white turbidity at the time of producing a molded plate can be reduced, and an overlay base paper excellent in transparency can be obtained. A decorative board can be manufactured. This decorative board can be suitably used as a material for building materials, furniture and the like.

Claims (1)

A natural pulp fiber having a degree of polymerization of 860 or more and an α-cellulose content of 85 to 92% by weight is adjusted to a Canadian standard freeness of 550 to 800 ml, and polyamide polyamine epithelium is added to 100 parts by weight of the natural pulp fiber. A method for producing an overlay base paper, comprising wet-making a pulp slurry to which 0.3 to 2.0 parts by weight of a chlorohydrin-based wet paper strength agent is added.