JPH01234427A - White sheet material - Google Patents

Abstract

PURPOSE:To obtain the subject material having excellent surface-smoothness and whiteness and having excellent dispersibility of white inorganic fine powder, by using a composition produced by compounding a polyester resin with a specific amount of CaCO3 or barium sulfate added with spherical fine powder of acrylic resin. CONSTITUTION:The objective material can be produced by compounding (A) 70-90wt.% of a polyester with (B) 10-30wt.% of calcium carbonate or barium sulfate added with spherical fine powder of acrylic resin composed mainly of polymethyl methacrylate, forming a sheet from the obtained polyester resin composition and drawing the sheet in at least one direction. The material is preferably produced by heating the components A and B at a temperature above the melting point of the component A, melting and kneading the mixture to uniformly disperse the component B into the component A, forming the dispersion in the form of a sheet and drawing the sheet in at least one direction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a white sheet material mainly composed of a polyester resin that has good dispersibility of white inorganic fine powder, excellent surface smoothness, and excellent white color.

(Prior Art/Technology) Synthetic paper made from thermoplastic resin has conventionally been manufactured using various methods, including a method in which the surface of an extruded film is roughened using an embossing roll, a method in which the surface of the film is immersed in a solvent and whitened. , a method of coating the film surface with an inorganic whitening agent such as calcium carbonate, and a method of extruding a resin filled with inorganic fine powder to form a film or sheet are known.

Among them, a method is already known in which an inorganic filler is blended in advance with a polyolefin resin or a polyethylene resin such as polyethylene or polypropylene, and then the sheet itself is made into a paper-like material (Japanese Patent Publication No. 46-197). 4346
Publication No. 8, Publication No. 48-3902, Publication No. 55-3001
4) and is widely applied industrially. This method is extremely interesting in that synthetic paper can be obtained in principle through a simple process of simply molding resin into a sheet.

(Problems to be Solved by the Invention) When polyolefin resin is used as a material, it is advantageous in that it has excellent film formability, is strong, has excellent chemical resistance, and is inexpensive, but it has low rigidity. As a sheet or film, it also has drawbacks such as weak stiffness, poor dimensional stability, and poor heat resistance.To overcome these drawbacks, it is necessary to incorporate a large amount of filler and laminate it with a biaxially oriented sheet. However, in the former case, if the amount added is increased, the dispersion of the filler in the resin becomes poor and the surface smoothness of the sheet deteriorates, and in the latter case, steps such as lamination are required, making the process complicated.

The present invention has been made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a white sheet material that has excellent mechanical properties, as well as excellent dispersibility of calcium carbonate or barium sulfate fine powder and flat surface smoothness. It's about doing.

(Means for solving the problem) The above purpose was achieved by adding spherical acrylic fine powder mainly composed of polymethyl methacrylate to 70-90% by weight of polyester resin and calcium carbonate or barium sulfate.
This is achieved by a white sheet material characterized in that a sheet of a polyester resin composition comprising 0 to 30% by weight is stretched in at least one direction.

In the present invention, a polyester resin with excellent mechanical properties, dimensional stability, and heat resistance is used, but any resin that can be formed into a sheet may be used, such as polyethylene terephthalate,
Examples include polybutylene terephthalate, polypropylene terephthalate, polyethylene-46-naphthalene dicarboxylate, and the like. Of course, these polyesters may be homopolyesters or copolyesters. Examples of copolymerization components include dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, and naphthalene dicarboxylic acid, and diol components such as ethylene glycol, neopentyl glycol, and polyalkylene glycol. As the polyester resin used in the present invention, polyethylene terephthalate is preferable, and (phenol/tetrachloroethane (60/
Most preferably, polyethylene terephthalate has an intrinsic viscosity of 0.5 to 0.9 as measured in a mixed solvent at 20° C. with a ratio of 4 ON amounts.

Calcium carbonate used in the present invention includes natural chalk,
It may be either a crushed product of limestone or marble or a synthetic product obtained by a chemical precipitation method. As barium sulfate, both natural products produced by crushing barite and synthetic products of precipitated barium sulfate synthesized from soluble salts can be used. These particle sizes are 0.1 to 1 as an average particle size.
Preferably, it is 0μ. If the particle size is 0.1 μm or less, whitening will be poor, while if it is 10 μm or more, the surface smoothness of the sheet will deteriorate. Note that the average particle size is measured by methods such as electron microscopy, sedimentation method, and transmission method.

In the present invention, calcium carbonate or barium sulfate (hereinafter simply referred to as filler) is used to further increase the whiteness of the sheet due to the voids that are generated around the interface with the resin by stretching after sheet molding. , it becomes possible to obtain a whiteness with an L value of 92 or more, or even 93 or more.

Conventionally, as a method of improving the surface smoothness of a thermoplastic resin sheet containing a large amount of inorganic filler, the surface of the inorganic filler has been treated to make it lipophilic.However, in the present invention, calcium carbonate or It is much more effective and preferable to use barium sulfate after being treated to make it lipophilic. In order to improve the surface smoothness of the sheet, it is necessary to uniformly disperse the resin 1' arches and the filler, thereby making the filler surface lipophilic.

Spherical acrylic fine powder is mainly made of polymethyl methacrylate, and has a large particle size of several tens to several 100 microns, which is conventionally used in paints, coating materials, adhesives, dental materials, molding materials, etc. It is not a thing, but the above 0.1~
In order to effectively act on a 10 μm filler, particles with a particle size of 1 micron or less are effective. Adding spherical acrylic fine powder to calcium carbonate or barium sulfate,
The exact reason why it is effective in improving the surface smoothness of the sheet is unknown, but by adding it (tri-blend), each particle of calcium carbonate or barium sulfate is loosened, and as a result, it enters the resin. It is assumed that this is because the dispersion of is improved. The amount of the spherical acrylic fine powder added is usually 10% by weight or less based on calcium carbonate or barium sulfate.

The polyester resin composition of the present invention comprises polyester 70
-90% by weight and 10-30% by weight of the above powder mixture. If the powder mixture is less than 10% by weight, sufficient whiteness cannot be obtained, whereas if it exceeds 30% by weight, the whiteness will be saturated and the physical properties of the sheet material will deteriorate.

In addition, in the present invention, heat stabilizers, plasticizers, antistatic agents,
A fluorescent whitening agent or the like may also be added if necessary.

Next, a method for manufacturing a white sheet of the present invention will be explained.

Calcium carbonate or barium sulfate is uniformly mixed with a small amount of spherical acrylic powder, and the polyester resin is heated to a temperature higher than the melting temperature of the polyester resin and melt-kneaded to form the filler into the polyester resin. The fine powder is uniformly dispersed and formed into a sheet. The sheet is then stretched in at least one direction, typically 100-500%. Stretching may be carried out in multiple stages or in two or more axial directions. Biaxial stretching may be carried out simultaneously or simultaneously. In the case of polyethylene terephthalate, stretching is carried out at a low temperature above the secondary transition point (preferably in the range of about 80 to 100 C) within a range that does not hinder the stretching, to prevent the formation of voids in the fine filler powder in the sheet. It is possible to improve the whiteness.

To add and mix spherical acrylic fine powder to calcium carbonate or barium sulfate, use a rotating container (tumbler, etc.)
The mixing machine is not limited to a fixed container type (Henschel mixer, etc.), or a composite type mixer.

For molding, the polyester resin and fine filler powder are sufficiently kneaded using a Banbury mixer and mixing roll.
A method in which a molten composition is molded by calender rolls, in which polyester resin and fine filler powder are continuously fed into a single-screw or twin-screw kneading extruder, melted and kneaded in the extruder, and molded into a sheet. There are a number of methods, including a method of molding into a tube shape by inflation molding, and the method is not limited to any one method. However, in the present invention,
To prevent deterioration of the polyester resin, polyester resin and a mixture of calcium carbonate or barium sulfate and spherical acrylic fine powder are separately and continuously fed into a twin-screw kneading extruder, and the fine powder is melted in a short time. A preferred method is to uniformly disperse the resin in the resin and then extrude and mold it.

(Effects of the Invention) The white sheet of the present invention has excellent whiteness and surface smoothness, and is extremely useful as high-grade synthetic paper for heat-resistant labels, sticker-1 copying paper, and the like.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

The evaluation method for the sheet is as follows.

α) Whiteness Measured using a Tokyo Juishiki Hunter White Photometer TR-600 in accordance with JIS-P8123.

(2) Surface smoothness The surface unevenness was visually determined.

○: Smooth with no unevenness observed.

Δ: Slight irregularities are observed here and there.

×: Unevenness is clearly observed.

(3) Particle dispersion The presence or absence of coarse particles of 10 μm or more was determined using an electron microscope with a magnification of 4000 times.

Example 1 3% by weight of spherical acrylic fine powder (manufactured by Soken Kagaku Co., Ltd., particle size 0.15μ) was added to barium sulfate (surface treated with glycerol monostearate, average particle size 0.3μ), and uniformly mixed using a Henschel mixer. mixed with.

The above mixture was subjected to twin-screw kneading extrusion t3<Japan Steel Works, TEX
-30) at a ratio of 20% by weight to polyethylene terephthalate resin (intrinsic viscosity 0.75),
The resin was heated to 0.degree. C., melted and kneaded, barium sulfate was uniformly dispersed in the resin, and then pelletized.

The resulting pellet was then dried and extruded from a remelted Reslit die onto a quenching rotating drum to form an amorphous sheet.
Using a biaxial stretching device, the stretching temperature is 90°C and the length and width are 2 at the same time.
00% stretching (stretching ratio 3:1). The thickness of the obtained film is 0.061EI.

Comparative Example 1 A stretched sheet was produced in the same manner as in Example 1, except that the spherical acrylic fine powder was not used.

The above results are shown in Table 1.

Example 2 Calcium carbonate (surface treated with fatty acid, average particle size 0.15
9% by weight of spherical acrylic fine powder was added to Example 1
A stretched sheet was produced in the same manner as above.

Comparative Example 2 A stretched sheet was produced in the same manner as in Example 2, except that the spherical acrylic fine powder was not used.

Example 3 A stretched sheet was produced in the same manner as in Example 2, except that the sheet was not surface-treated with calcium carbonate.

Comparative Example 3 A stretched sheet was produced in the same manner as in Example 3, except that the spherical acrylic fine powder was not used.

The above results are also shown in Table 1. In contrast to Comparative Examples 1 to 3, Examples 1 to 3 of the present invention were all films with excellent opacity, whiteness, and surface smoothness, and in particular, surface-treated l-calcium and sulfurized barium were used. Example 1
and 2 are surface smoothness procedural amendments (methods) July 19, 1988 Patent Application No. 62328 of 1988 2, Title of invention White sheet material 3, Relationship with the person making the amendment Patent applicant address Tokyo 5-17-4 Sumida, Sumida-ku, Miyako 534
Patent Department, Kanebo Co., Ltd., 1-5-90 Tomobuchi-cho, Bejima-ku, Osaka City Telephone (06) 921-1251 5. Column 6 of "Detailed Description of the Invention" of the specification to be amended, Contents of the amendment (1) ) On page 1 of the specification, between lines 14 and 15, write "3. Detailed Description of the Invention" and the description of the item on one line.

that's all

Claims (2)

[Claims] (1) Few sheets of a polyester resin composition consisting of 70-90% by weight of polyester and 10-30% by weight of calcium carbonate or barium sulfate to which spherical acrylic fine powder mainly composed of polymethyl methacrylate is added. A white sheet material characterized by being stretched in both uniaxial directions. (2) The material according to claim 1, wherein the calcium carbonate or barium sulfate is subjected to a lipophilic surface treatment.