JP2008081898A - Decorative sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a decorative sheet high in peel strength, slight in mechanical strength drop even if wetted with water for a long period of time, and preferably usable as a surface material formed into a decorative board by being laminated on a substrate such as a plywood, particle board or medium-density fiberboard, in particular as a surface material for floorings used at places where water is used, including kitchens and lavatory. <P>SOLUTION: The decorative sheet is obtained by impregnating base paper including pulp composed of 80-50 wt.% of wood-based pulp and 20-50 wt.% of polyethylene-based synthetic pulp and 5-15 wt.% of a filler based on the pulp, with 25-70 wt.% of an acrylic resin based on the base paper, and heat treated at a temperature higher than the melting point of the polyethylene-based synthetic pulp. The decorative sheet thus obtained has a peel strength between paper layers after immersed in water for 24 h of 130 N/m or higher. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention performs solid printing and pattern printing with a gravure printing machine, and is laminated on a base material such as plywood, particle board, medium fiber board, etc. to make a decorative board, surface material for building materials or furniture, particularly kitchens, The present invention relates to a decorative sheet used for a surface material for flooring used in a place where water is used such as a toilet.

The decorative sheet base material is classified into a type based on paper using thin paper, reinforced paper, impregnated paper, and the like, and a type using a film using a vinyl chloride film, a polyolefin film, or the like. In recent years, in consideration of environmental problems and the like, a shift from a film to a paper-based type, in particular, a type using impregnated paper from the aspect of strength and processability is progressing.
However, impregnated paper has the drawback of peeling between paper layers as compared to film, and furthermore, when wetted with water, the strength is greatly reduced. For example, high peel strength such as floor surface, high surface strength, water resistance, moisture resistance Use has been limited to the necessary parts.

In order to obtain high peel strength, high surface strength, or to improve water resistance, a sheet having a protective layer on the surface of a base paper has been reported (Patent Document 1). However, not only is the process complicated to provide the protective layer, but also the problem is that when it is immersed in water for a long time, water enters from the end of the paper and the strength reduction cannot be sufficiently suppressed. there were.
Thus, studies on base papers have been conducted. For example, Patent Document 2 discloses a method using a water-impregnated impregnating resin, but the main cause of the decrease in water resistance is due to cellulose constituting the pulp. Therefore, there has been a problem that when it gets wet for a long time, the strength decreases. Patent Document 3 proposes a method for obtaining good water resistance by blending synthetic fibers and then heat-sealing them. However, in order to heat-synthesize synthetic fibers after papermaking, a resin is used in the impregnation process. There was a drawback that it was not possible to obtain a high peel strength because it did not sufficiently enter the inside of the layer.
JP-A-7-331594 JP-A-5-195491, JP-A-11-58622, JP-A-2002-147004 Japanese Patent Laid-Open No. 6-136585

  An object of the present invention is to solve such a conventional problem, and in particular, to provide a decorative sheet having a high peel strength and little reduction in strength even when wet.

This invention discovered that what heat-processed the specific impregnated paper can solve the said subject.
That is, the present invention
(1) A base paper containing an acrylic resin on a base paper containing 80 to 50% by weight of a wood-based pulp and 20 to 50% by weight of a polyethylene-based synthetic pulp and a filler of 5 to 15% by weight with respect to the pulp. A decorative sheet having a paper delamination strength of 130 N / m or more after being immersed in water for 24 hours, impregnated with 25 to 70% by weight, and then heat-treated at a temperature equal to or higher than the melting point of the polyethylene synthetic pulp;
(2) The decorative sheet according to (1), wherein the decorative sheet is for flooring,
Is to provide.

  The decorative sheet of the present invention has high peel strength, and even when it is wet for a long time, there is little decrease in strength. Therefore, it can be suitably used as a decorative sheet for a surface material for flooring used in places where water is used, such as kitchens and toilets.

The base paper used in the present invention is a paper made by mixing 80 to 50% by weight of wood pulp and 20 to 50% by weight of polyethylene synthetic pulp with 5 to 15% by weight of filler based on the pulp. is there.
Wood-based pulp can contain LBKP alone or NBKP as necessary. The beating degree of the wood pulp is desirably 500 to 600 mlcsf. If it is less than 500 mlcsf, beating progresses too much, impregnation becomes worse, and high peel strength cannot be obtained. On the other hand, if it exceeds 600 mlcsf, the beating is insufficient and the smoothness of the paper is low, which is not preferable from the viewpoint of printability.

A polyethylene synthetic pulp having a melting point of about 120 to 140 ° C. is used. If the melting point is less than 120 ° C., it tends to get dirty in the drying process, and it is not preferable from the viewpoint of the heat resistance of the paper. On the other hand, when the melting point is 140 ° C. or higher, a high temperature is required for heat-sealing by heat treatment after impregnation, and there is a problem that the paper turns yellow.
Examples of such polyethylene fibers include synthetic pulp such as SWP manufactured by Mitsui Chemicals, Inc. These may be blended with two or more types having different melting points, fiber lengths, fiber diameters, and the like.
If the polyethylene synthetic pulp is less than 20% by weight, the effect of increasing the water resistance is insufficient. On the other hand, if it exceeds 50% by weight, the wet strength is low, causing a problem of running out of paper at the time of impregnation and not preferable in terms of cost.

  Examples of the filler used in the present invention include white fillers typified by titanium dioxide or organic and inorganic color pigments for providing shielding properties to the base paper. When the addition amount is less than 5% by weight with respect to the pulp, the shielding property is not sufficient, and when it exceeds 15% by weight, the shielding property is improved, but high peel strength is hardly obtained, which is not preferable.

  For decorative sheets, wet paper strength agents such as polyamide polyamine epichlorohydrin (hereinafter abbreviated as PAE), paper strength enhancers such as carboxymethylcellulose, starch and polyacrylamide, sulfate bands, yields of polymer flocculants, etc. An improver, an antifoaming agent, etc. can be added as needed.

  The base paper is made by a wet paper making method according to a conventional method.

The base paper is impregnated with acrylic resin in an amount of 25 to 70% by weight (20 to 41% as the impregnation rate), more preferably 30 to 60% by weight (23% to 37.5% as the impregnation rate).
If the acrylic resin is less than 25% by weight, a high peel strength cannot be obtained, and if it exceeds 70% by weight, it tends to become dirty in the process, which is not preferable from the viewpoint of blocking and cost.
As the acrylic resin to be used, those obtained by copolymerizing acrylic acid and its ester, methacrylic acid and its polymer and copolymer, acrylonitrile, acrylamide, styrene and the like can be used. As these acrylic resins, soap-free emulsion-polymerized acrylic resins, acrylic resins internally crosslinked with an internal crosslinking agent, and acrylic resins self-crosslinked with a self-crosslinking agent can be used.
Moreover, there is no problem even if a styrene-butadiene rubber-based resin or a methyl methacrylate-butadiene rubber-based resin is mixed and used.
The impregnation method may be either an in-line impregnation method after paper making by a size press or the like, or a method of once dip impregnation offline after paper making and drying.

In this invention, it heat-processes at the temperature more than melting | fusing point of a polyethylene-type synthetic pulp after an impregnation.
As conditions for the heat treatment, it is preferable to perform heat treatment at a temperature equal to or higher than the melting point of the polyethylene-based synthetic pulp, for example, 130 ° C. for 1 minute or longer.
The heat treatment may be performed before or after the calendar treatment as long as it is after impregnation.

The decorative sheet of the present invention has a paper delamination strength of not less than 130 N / m, preferably not less than 150 N / m after being immersed in water for 24 hours. In addition, the paper delamination strength after water immersion as used in the field of this invention means the intensity | strength measured in the wet state at the time of peeling in a T-shape in the middle of a paper layer.
When the paper interlayer peel strength is less than 130 N / m, when used as a surface material used in a place where water is used, the peel strength may decrease and the paper may be peeled off between paper layers.
In the present invention, the paper delamination strength of a reinforced paper (decorative sheet) for a general decorative board is about 100 N / m, and even when immersed in water for 24 hours, the paper delamination strength is 130 N / m or more. For example, it has been found that even if it is used as a surface material used in a place where water is used, it has sufficient peel strength and is preferably used.

  The decorative sheet of the present invention preferably has a smoothness of 300 seconds or more, which has been smoothed after impregnation. It is particularly desirable to use a heat calendar method for the smoothing process. In the heat calendar system, the calendar roll temperature is preferably set to 80 to 120 ° C. When the temperature is less than 80 ° C., the smoothness is lowered. On the other hand, when the temperature is more than 120 ° C., the calendar stain is deteriorated.

Examples of the present invention will be described in detail below.
In addition, the characteristic of the decorative sheet in an Example was evaluated with the following method.
(1) Impregnation rate: calculated by the formula [1].

(2) Paper delamination strength: cut out in 15 mm width in the MD direction of paper, peeled into a T-shape so as to be peeled between paper layers, and the strength at that time was measured with a Tensilon universal testing machine (PTM-100 made by Orientec) It was measured.
(3) Paper delamination strength after 24 hours of water immersion: A measurement sample prepared in the same manner as the method for measuring the paper delamination strength was immersed in water at 23 ° C. for 24 hours. Then, it was taken out from the water, wiped off excess moisture with blotting paper, peeled into a T-shape so as to be peeled off between paper layers, and the strength at that time was measured with a Tensilon universal testing machine (PTM-100 manufactured by Orientec). .

Example 1
80 parts by weight of LBKP / NBKP (20/80) beaten to 600 mlcsf with a refiner, 20 parts by weight of polyethylene-based synthetic pulp (manufactured by Mitsui Chemicals, SWP E790) having a melting point of 135 ° C., 10 parts by weight of color pigments, and various paper making aids (Wet paper strength agent PAE 2 parts by weight, aluminum sulfate 3 parts by weight, sodium aluminate 0.5 parts by weight) was internally added, and a base paper was made by a wet paper making method by a conventional method. The drying temperature of the base paper was 100 ° C. and was adjusted to a temperature below the melting point of the polyethylene synthetic fiber.
This base paper was impregnated with an acrylic resin (Nipol LX814, manufactured by Nippon Zeon Co., Ltd.) so that the impregnation rate was 25.8 wt%. Next, after heat-treating the fibers at 140 ° C. for 2 minutes to heat-seal the fibers, smoothing treatment was performed with a super calender to produce a decorative sheet having a smoothness of 300 seconds.

Example 2
The same procedure as in Example 1 was performed except that a polyethylene synthetic pulp having a melting point of 120 ° C. (manufactured by Mitsui Chemicals, SWP AU690) was used instead of the one having a melting point of 135 ° C. (impregnation rate: 26. 5%), a decorative sheet was prepared.

Example 3
In Example 1, the addition amount of LBKP / NBKP (20/80) was changed to 80 parts by weight, 50 parts by weight, the addition amount of the polyethylene synthetic pulp was changed to 20 parts by weight, and the impregnation rate was changed to 50 parts by weight. A decorative sheet was produced in the same manner as in Example 1 except that the content was 34.8%.

Example 4
In Example 2, the addition amount of LBKP / NBKP (20/80) was changed to 80 parts by weight and 50 parts by weight, and the addition amount of the polyethylene synthetic pulp was changed to 20 parts by weight, and the examples were changed to 50 parts by weight. 1 (impregnation rate 25.5%), a decorative sheet was produced.

Example 5
A decorative sheet was produced in the same manner as in Example 3 except that the heat treatment time in Example 3 was changed to 5 minutes instead of 2 minutes.

Comparative Example 1
A decorative sheet was produced in the same manner as in Example 2 (impregnation rate: 25.2% by weight) except that the heat treatment was replaced after the acrylic resin impregnation and the base paper was not impregnated with the acrylic resin.

Comparative Example 2
A decorative sheet was produced in the same manner as in Example 2 except that the impregnation ratio of the acrylic resin in Example 1 was 19.0% by weight.

Comparative Example 3
A decorative sheet was produced in the same manner as in Example 1 (impregnation rate: 28.2% by weight) except that polyethylene synthetic pulp was not used as pulp and only 100 parts by weight of wood pulp was used.

Table 1 shows the characteristics of the decorative sheets obtained in Examples and Comparative Examples.
The decorative sheets prepared in Examples 1 to 4 have a high peel strength with a paper delamination strength of 300 N / m or more, and the paper delamination strength after immersion in water for 24 hours is also a strength of 150 N / m or more. was gotten. The value of the paper delamination strength after immersion in water is the level of the paper delamination strength of the impregnated paper used for the decorative board, and the decorative sheet of the present invention has a strength that does not easily peel even when wet. I understand that.
On the other hand, the decorative sheet produced in Comparative Example 1 has a low paper delamination strength because it has a substantially similar impregnation rate due to heat fusion of polyethylene synthetic pulp before impregnation, but the paper delamination strength is low. Only a low strength of about 100 N / m was obtained for the paper delamination strength after time immersion in water.
Moreover, the decorative sheet produced in Comparative Example 2 had a low impregnation rate, and both the paper delamination strength and the paper delamination strength after 24 hours of water immersion were low.
The decorative sheet produced in Comparative Example 3 obtained a high paper delamination strength, but the paper delamination strength after 24 hours of water immersion was insufficient.

  The decorative sheet of the present invention has a high peel strength, and has little decrease in strength even when wet for a long time. The surface of the decorative sheet is bonded to a base material such as plywood, particle board or medium fiber board. It can be suitably used as a surface material for flooring materials used in places where water is used, particularly in places such as kitchens and toilets.

Claims (2)

  A base paper containing 80 to 50% by weight of wood-based pulp and 20 to 50% by weight of polyethylene-based synthetic pulp, and 5 to 15% by weight of filler with respect to the pulp, acrylic resin to the base paper A decorative sheet impregnated with 25 to 70% by weight and then heat-treated at a temperature equal to or higher than the melting point of the polyethylene synthetic pulp and having a paper delamination strength of 130 N / m or more after 24 hours of water immersion.   The decorative sheet according to claim 1, wherein the decorative sheet is for flooring.