JP2002036353A - Method for manufacturing biaxially stretched aromatic vinyl resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a biaxially stretched sheet generating no gel or air bubbles at the time of extrusion processing, hard to generate breaking at the time of stretching processing and excellent in mold reproducibility and deep drawing properties at the time of secondary processing. SOLUTION: In the method for manufacturing the biaxially stretched aromatic vinyl resin sheet, a mixture (I), which comprises (A) a copolymer of an aromatic vinyl compound and a carboxyl group or acid anhydride group-containing unsaturated monomer, for example, a styrene/methacylic acid copolymer and (B) an organic compound having one hydroxyl group, for example, stearyl alcohol, is melted and kneaded in an extruder and the kneaded mixture is extruded from a T-die and the extrudate is biaxially stretched.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a biaxially stretched sheet comprising a copolymer (A) of an aromatic vinyl resin compound and a carboxyl group or acid anhydride group-containing unsaturated monomer. While maintaining excellent properties such as heat resistance, high temperature oil resistance, transparency, and rigidity of the copolymer (A), it suppresses gelation by dehydration cyclization reaction during extrusion melting and generation of bubbles due to decomposition reaction, The present invention relates to a method for producing a biaxially stretched sheet, which provides stable stretchability and further improves secondary formability such as air pressure moldability.

[0002]

2. Description of the Related Art Hitherto, biaxially stretched polystyrene sheets have been widely used in lightweight containers for foods because of their excellent transparency, secondary workability, rigidity, and low cost. But,
The biaxially stretched polystyrene sheet was inferior in heat resistance and high-temperature oil resistance, and could not be used for applications in direct contact with boiling water or for oily food containers reheated in a microwave oven.

To improve the heat resistance of a biaxially stretched polystyrene sheet, there is a styrene-maleic anhydride copolymer, which deforms in boiling water at 100 ° C., is filled with an oily food, and heated in a microwave oven. In such a case, there was a defect such as whitening deformation due to poor high temperature oil resistance. Also,
Japanese Patent Publication No. 60-54383 discloses a styrene-methacrylic acid copolymer (SMAA resin) obtained by copolymerizing a styrene monomer and a methacrylic acid monomer. There has been a problem that dehydration cyclization reaction occurs due to heat generation and the like, and gels and bubbles are generated.

Further, the styrene-methacrylic acid copolymer has a low elongation at break in a rubber-like elastic region to be oriented and is inferior in ductility, so that it is easily broken during stretching. In addition, when the biaxially stretched sheet is subjected to secondary forming such as hot plate press forming, there is a problem that mold reproducibility and deep drawability are poor.

[0005]

An object of the present invention is to provide a copolymer of an aromatic vinyl compound and an unsaturated monomer containing a carboxyl group or an acid anhydride group, for example, styrene-methacrylic acid copolymer. A biaxially stretched aromatic vinyl sheet using a coalesced product. The dehydration cyclization reaction due to shear heat generation during extrusion processing is unlikely to occur, no gel or bubbles are generated, and it is difficult to break during stretching processing. An object of the present invention is to provide a method for producing a biaxially stretched sheet that is excellent in mold reproducibility and deep drawability during the next processing.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the copolymerization of an aromatic vinyl compound with an unsaturated monomer having a carboxyl group or an acid anhydride group is possible. A mixture (A), for example, a mixture (I) of a styrene-methacrylic acid copolymer and an organic compound (B) having one hydroxyl group is melt-kneaded with an extruder, and then extruded from a T-die and biaxially stretched. Since dehydration cycling reaction due to shear heat generation during processing is unlikely to occur, no gel or bubbles are generated, stretching is stable and difficult to break, and secondary workability is improved, mold reproducibility and deep drawing It has been found that a biaxially stretched aromatic vinyl resin sheet having excellent properties can be obtained, and the present invention has been completed.

That is, the present invention provides: A mixture (I) of a copolymer (A) of an aromatic vinyl compound, a carboxyl group or an acid anhydride group-containing unsaturated monomer, and an organic compound (B) having one hydroxyl group is melt-kneaded with an extruder. And then extruding from a T-die and biaxially stretching, a method for producing a biaxially oriented aromatic vinyl resin sheet, 2. The method for producing a biaxially oriented aromatic vinyl resin sheet according to the above 1, wherein the organic compound (B) having one hydroxyl group is an aliphatic alcohol having 1 to 40 carbon atoms. The organic compound (B) having one hydroxyl group is selected from the group consisting of cetyl alcohol, stearyl alcohol and triethylene glycol monomethyl ether.
3. The method for producing a biaxially stretched aromatic vinyl resin sheet according to the above 1, which is at least one kind of alcohol; After the melt-kneading, after extruding from a T-die, longitudinal stretching (uniaxial stretching step) is performed by a speed difference between rolls, and then transverse stretching (biaxial stretching step) with a tenter, the biaxial as described in the above 1, 2 or 3 4. a method for producing a stretched aromatic vinyl resin sheet; The compounding amount of the organic compound (B) having one hydroxyl group is
0.001 to 3 based on 100 parts by weight of the copolymer (A)
5. The method for producing a biaxially stretched aromatic vinyl resin sheet according to any one of the above 1 to 4, which is a part by weight; Biaxial stretching temperature is (Tg-5)-(Tg + 20) ° C
[However, Tg is the main dispersion temperature of the mixture (I). And the longitudinal stretching speed is 50 to 300% / sec.
6. The method for producing a biaxially stretched aromatic vinyl-based resin sheet according to 4 above, wherein the transverse stretching speed is 2 to 80% / sec, and The method for producing a biaxially stretched aromatic vinyl resin sheet according to any one of the above 1 to 6, wherein the copolymer (A) is a styrene- (meth) acrylic acid copolymer. It is.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The copolymer (A) used in the present invention is a copolymer of an aromatic vinyl compound and an unsaturated monomer having a carboxyl group or an acid anhydride group, and is not particularly limited.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 1,3
-Dimethylstyrene, 2,4-dimethylstyrene, t-
Examples thereof include monomers such as butylstyrene and mixtures thereof, and among them, styrene and α-methylstyrene are preferred from the viewpoints of transparency, processability, cost and the like of the stretched sheet.

The unsaturated monomer containing a carboxyl group or an acid anhydride group includes, for example, acrylic acid, methacrylic acid, maleic anhydride or derivatives thereof. Among them, heat resistance and oil resistance at high temperatures are improved. And methacrylic acid is preferred in terms of cost and cost. Further, a part of methacrylic acid may be replaced with α-methylstyrene in order to reduce the viscosity of the copolymer and improve the moldability.

The content of the unsaturated monomer containing a carboxyl group or an acid anhydride group is not particularly limited,
The range of 3 to 30% by weight is preferable from the viewpoint of heat resistance, high-temperature oil resistance, and extrusion stretching processability.
The range of 5 to 15% by weight is particularly preferable from the viewpoint of compatibility of high-temperature oil resistance performance.

Examples of the organic compound (B) having one hydroxyl group include, for example, R-OH (where R is a hydrogen atom or a carbon atom having 1 to 4 carbon atoms).
0, an alkyl group, an aryl group, an arylalkyl group,
Represents an alkoxy group or a polyalkoxy group, and -OH is primary or secondary. ).

The organic compound (B) having one hydroxyl group includes, for example, methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, secondary butyl alcohol, isoamyl alcohol, n-amyl alcohol, neopentyl alcohol, n-hexyl alcohol, n-octyl alcohol, 2-octyl alcohol, dodecyl alcohol, cetyl alcohol, stearyl alcohol, myristyl alcohol, 2phenylethanol, p-methylbenzyl alcohol, nonylphenol, dodecylphenol , 2-methoxyethanol,
2-ethoxyethanol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monomethyl ether, ethoxylated nonylphenol, and the like. One or two or more kinds are mixed. Can be used. Among these, aliphatic alcohols having 1 to 40 carbon atoms are preferable from the viewpoint of the efficiency of suppressing gels and bubbles during extrusion processing, and further, from the viewpoint of bleed out and odor in the sheet, those having 10 to 20 carbon atoms are preferable. Aliphatic alcohols are more preferred.

The amount of the organic compound (B) having one hydroxyl group is usually 0.001 to 3 parts by weight with respect to 100 parts by weight of the copolymer (A). The effect of suppressing the reaction is high. Further, the range of 0.01 to 2 parts by weight is particularly preferable because the cyclization reaction and the decomposition reaction at the time of extrusion processing are suppressed while maintaining heat resistance and oil resistance, and furthermore, odor or bleed-out does not occur. .

Various antioxidants may be added to the copolymer (A) in combination with the organic compound (B) having one hydroxyl group.

As the antioxidant, for example, triethylene glycol-bis [3- (3-tert-butyl-5-
Methyl-4-hydroxyphenyl) propionate],
n-octadecyl-3-(-4'-hydroxy-3 ',
5'-di-tert-butylphenyl) propionate,
1,1,3-tris- (2-methyl-4-hydroxy-
Hindered phenolic antioxidants such as 5-tert-butylphenyl) butane. Further, dimyristyl-3,3'-thiodipropionate, pentaerythritol-tetrakis- (β-lauryl-thiopropionate) or the like may be used in combination with the above hindered phenolic antioxidant. Further, if necessary, other antioxidants, ultraviolet absorbers, heat stabilizers, plasticizers, anti-fog agents, lubricants, dyes / pigments, freshness preservatives, antibacterial agents, gas adsorbents, release agents, etc. are polymerized. It may be added at the time or in a pelletizing step after polymerization. These additives may be used alone or in combination of two or more.

The copolymer (A) of the aromatic vinyl compound and the unsaturated monomer having a carboxyl group or an acid anhydride group includes, in addition to the organic compound (B) having one hydroxyl group, a sheet and a secondary molding. In order to improve the stacking property of the product, inorganic particles (C) and organic particles (D) can be added.

The particle size of the inorganic particles and the organic particles is not particularly limited, but is preferably 1% in order to improve the anti-stacking property without impairing the transparency of the sheet.
It is preferably 0 μm or less. Further, the thickness is more preferably from 2 to 6 μm while suppressing the whitening due to crazing that occurs in the deep drawing in which the linear drawing ratio exceeds 3 in the secondary molding while maintaining the anti-stacking property.

Further, the shape of the inorganic particles or the organic particles is preferably one having an aspect ratio of 1 to 1.5 in order to make the surface of the stretched sheet uniformly uneven or to easily produce projections on the surface during stretching. Among them, spherical particles are particularly preferable because projections on the surface of the copolymer (A) are likely to appear uniformly. Depending on the application, an indefinite one can also be used as appropriate.

As the inorganic particles, for example, silicon oxide,
Examples include calcium carbonate and silicon particles. Also,
As the organic particles, for example, cross-linked polystyrene particles,
And polymethyl methacrylate particles.

The amount of the inorganic or organic particles is appropriately adjusted according to the use of the biaxially stretched sheet, but is preferably 0.01 to 0.5 parts by weight based on 100 parts by weight of the copolymer (A). Is preferable because both transparency and anti-stacking property are achieved. As a method for adding these particles, there is a method in which the particles are kneaded and blended with the copolymer (A) in advance, a method in which a master batch is prepared in advance, and a method in which the particles are directly blended during extrusion biaxial stretching. is there.

The degree of dispersion of the copolymer (A) (the ratio between the weight average molecular weight Mw and the number average molecular weight Mn = Mw / Mn) is determined by the occurrence of gel due to a cyclization reaction during extrusion, sequential biaxial stretching, From the viewpoint of the extensibility in the secondary processing, the impact resistance of the stretched sheet and the tear strength, it is preferably from 1.5 to 4.5, more preferably from 2.0 to 3.5.

When the mixture (I) of the copolymer (A) and the organic compound (B) having one hydroxyl group (I) is melt-kneaded and extruded, it is preferable to use a vented single extruder or a twin-screw extruder. In particular, when the copolymer (A) is in the form of beads obtained by suspension polymerization, the mixture (I) to which various additives have been added is directly mixed with a twin-screw extruder because the formation of crosslinked gel and bubbles can be suppressed. Extrusion and stretch film formation methods can be used.

The temperature of the molten resin at the time of extrusion is adjusted to 210 to 270 ° C. in order to exert the effect of preventing cyclization and decomposition of the organic compound (B) having one hydroxyl group. It is preferable to select a kneading extruder having a ratio of 10% or less.

The step of melting the mixture (I) of the copolymer (A) and the organic compound (B) having one hydroxyl group and biaxially stretching the sheet is not particularly limited, but the sheet is extruded into a sheet. Thereafter, the film is uniaxially stretched in the machine direction by the speed difference between the rolls, and then biaxially stretched in the transverse direction by a tenter or the like.
The axial stretching method is preferable because there is a degree of freedom in adjusting the balance of the orientation degree in the vertical and horizontal directions and the sheet width.

The biaxial stretching of the mixture (I) is performed at a specific temperature and stretching speed in order to stably perform stretching, or to improve mold reproducibility and deep drawability in secondary working. It is preferable to perform stretching in the longitudinal and transverse directions. The copolymer (A) is inferior in stretchability in the rubbery elastic region compared to general polystyrene, so to improve stretchability and secondary workability, select stretching conditions. It is particularly important to do so.

In the longitudinal uniaxial stretching step, a method of performing orientation by a difference in roll speed is generally used. When the main dispersion temperature in the temperature dispersion curve obtained by the dynamic viscoelasticity measurement is Tg, the resin temperature is (Tg−5) to (Tg + 20) ° C.
The temperature is more preferably (Tg + 5) to (Tg + 15) ° C. in order to provide an appropriate degree of orientation for improving the secondary workability.

The stretching speed is preferably from 50 to 300% / sec, especially from 80 to 80%, since the copolymer (A) is easily torn in the rubber-like elastic region at the stretching temperature and has poor spreadability. 200% / sec is particularly preferable from the viewpoint of stable stretch film formation.

The stretching speed is defined by the following equation (1). (Si-So) / L × 100 (1) Si: Low-speed roll rotation speed (m / sec) So: High-speed roll rotation speed (m / sec) L: Distance between stretching

As the stretching method, the low-speed roll and the high-speed roll are rotated in the same direction to pass the resin flat, and the stretching is performed. The low-speed roll and the high-speed roll are rotated in reverse to pass the resin through the cloth. There is a stretching method, and any combination of single-stage or multi-stage, flat or cloth can be used.

In the transverse stretching step, it is preferable to set the stretching temperature to 2 to 80% / sec after setting the above resin temperature.
Among them, 10 to 50% / sec is particularly preferable from the viewpoint of stable stretch film formation.

Here, the stretching speed is defined by the following equation (2). [(Wo-Wi) / Wi × 100] / (L / S) (2) Wo: width before lateral stretching (m) Wi: width after stretching (m) L: distance from Wi to Wo S: Line speed (m / sec)

After the transverse stretching, it is preferable to heat set the stretched sheet while maintaining the tenter width at a temperature lower than the stretching temperature by 5 to 20 ° C. This is important in order to make uniform the alignment unevenness due to the bowing phenomenon or the like generated during the transverse stretching.

The stretching ratio can be set to a high value when the stretching temperature is high and to a low value when the stretching temperature is low. However, the stretching temperature and the ratio can be arbitrarily combined depending on the desired degree of orientation. Above all, the stretching ratio is preferably set to about 2 to 5 times, and more preferably 2.5 to 3.5 times from the viewpoint of productivity.

The biaxially stretched sheet of the copolymer (A) is given a maximum shrinkage stress of 0.2 to 2.0 MPa, more preferably 0.5 to 1.0 MPa, uniformly in the longitudinal and transverse directions under the above stretching conditions. Are preferred. The maximum shrinkage stress is an important factor from the mold reproducibility and the deep drawability during the secondary processing such as hot plate pressure forming and the mechanical strength of the biaxially stretched sheet.

[0036]

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the content of the present invention is not limited by these examples. All parts and percentages in the examples are on a weight basis unless otherwise specified.

Examples 1 to 3 The following copolymer mixtures (1) to (3) were each
The sheet is fed to a sheet forming machine equipped with a mm vent type extruder (L / D = 36, compression ratio 3.4), formed into a sheet at the extruded resin temperature shown in Table 1, and has a thickness of 900 μm. Then, under the conditions shown in Table 1, longitudinal stretching was performed with a difference in roll speed, and then transverse stretching was performed with a tenter to form a biaxially stretched sheet.

Copolymer mixture (1) Styrene-methacrylic acid copolymer (A-1) 100 parts (methacrylic acid content: 10%, Mw = 300,000, Mn = 120,000) Alcohol mixture (B-1) 0.05 part (mixture of 5% cetyl alcohol and 95% stearyl alcohol) Spherical silicon oxide (C-1) 0.02 part (average particle diameter 6.7 μm) Copolymer mixture (2) Styrene-methacrylic acid Copolymer (A-2) 100 parts (methacrylic acid content 15%, Mw = 240,000, Mn = 850,000) Stearyl alcohol (B-2) 0.1 part Spherical silicon oxide (C-2) 0.02 parts (average particle diameter 4.6 μm) Copolymer mixture (3) Styrene methacrylic acid copolymer (A-3) 100 parts (methacrylic acid content 20%, Mw = 260,000, Mn = 7. 60,000) Trietile Glycol monomethyl ether (B-3) 0.05 parts Amorphous silicon oxide (C-3) 0.03 parts (average particle diameter 2.3 μm)

The weight average molecular weight (Mw) of the styrene-methacrylic acid copolymer was measured by a light scattering method, and the number average molecular weight (Mn) was measured by an osmotic pressure method. The average particle diameter of silicon is measured by a laser diffraction method using SHIMAZU SALD2000 manufactured by Shimadzu Corporation.

Next, the copolymer mixture (1)
(3) The main dispersion temperature (Tg) measurement and gel / bubble test (test for confirming the degree of gel or bubble generation) are performed, and the basic physical properties (degree of orientation, tear strength) of the obtained biaxially stretched sheet are obtained. , Bending resistance, heat resistance, high temperature oil resistance, haze, gloss, tensile modulus) and hot plate pressure forming test of the biaxially stretched sheet were performed as follows. The results are shown in Table-3.

A copolymer mixture main dispersion temperature (Tg): measured using RSAII manufactured by Rheometrics Co., Ltd. in accordance with JIS P-7198. Gel / bubble test: Each of the copolymer mixtures (1) to (3) was supplied to a sheet forming machine equipped with a φ50 mm vent type extruder (L / D = 36, compression ratio 3.4). After the resin was extruded stably at the extrusion resin temperature shown in Fig. 1 at a discharge rate of 15 kg / hr, the screw rotation was stopped, and the screw was left as it was for 30 minutes. Immediately after raising, the unstretched sheet was observed for fisheye gel and bubbles, and evaluated according to the following criteria. ○ ・ ・ No fish-eye gel or bubbles due to decomposition reaction. ×: Gel or air bubbles with irregularities are generated on the sheet surface.

Biaxially stretched sheet Orientation degree: The stretched sheet was heated between hot plates (gap: 5 mm) set at 200 ° C., and the maximum shrinkage stress generated at that time was measured. Tear strength: Measured according to JIS P-8116. Bending resistance: Measured according to JIS P-8115. Heat resistance: A test piece of 100 × 100 mm was immersed in a silicone oil bath for 5 minutes, and the temperature at which either of the MD and TD contracted by 2% was measured. High-temperature oil resistance: White keep oil was applied to a sheet, and the appearance of the sheet after being left in a gear oven at 100 ° C. for 5 minutes was observed. ○ ・ ・ No change. ×: There are changes such as whitening, crazing, and holes. Haze: Measured according to JIS K-7105. Gloss: Measured according to JIS K-7105. Tensile modulus: Measured according to JIS K-7127. Hot plate press forming: Using a press forming machine PK400 manufactured by Kansai Automatic Machine Co., Ltd. and a mold of length × width × depth = 73 × 63 × 30 mm, hot plate temperature 130-150 ° C., heating time 2.5 seconds, molding Under the conditions of a time of 3 seconds and a molding pressure of 0.3 MPa, raindrops (raindrop-like shrinkage spots of about 2 to 15 mm due to excessive heating) occur from the minimum molding temperature at which mold reproducibility becomes 80% or more. The temperature range was measured and judged according to the following criteria.・: The temperature range is 6.5 ° C or higher. Δ: The temperature range is less than 6.5 to 3 ° C. ×: The temperature range is less than 3 ° C.

Comparative Examples 1 and 2 The following copolymer mixtures (1 ') to (2') were used in place of the copolymer mixture (1), except that they were biaxially stretched under the conditions shown in Table 2. In the same manner as in Example 1, a biaxially stretched sheet for comparison was formed into a film, and then the main dispersion temperature (Tg) of the copolymer mixtures (1 ′) to (2 ′) was measured in the same manner. The gel / bubble test (test to confirm the degree of gel and bubble generation) was performed, and the basic physical properties of the obtained biaxially stretched sheet for comparison and the hot-plate pressurization test of the biaxially stretched sheet were performed. . The results are shown in Table-4.

Copolymer mixture (1 ′) Styrene-methacrylic acid copolymer (A-1) 100 parts (methacrylic acid content 10%, Mw = 300,000, Mn = 120,000) Spherical silicon oxide (C -1) 0.02 parts (average particle size 6.7 μm)-Copolymer mixture (2 ') Styrene-methacrylic acid copolymer (A-2) 100 parts (methacrylic acid content 15%, Mw = 240,000) , Mn = 850,000) Spherical silicon oxide (C-2) 0.02 parts (average particle diameter 4.6 μm)

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

[Table 4]

[0049]

According to the production method of the present invention, no gel or bubbles are generated during the extrusion process, the stretching process is stable and difficult to break, and the secondary workability is improved, and the mold reproducibility is improved. And a biaxially stretched aromatic vinyl resin sheet having excellent drawability.

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Claims (7)

[Claims] 1. A mixture (I) of a copolymer (A) of an aromatic vinyl compound, an unsaturated monomer having a carboxyl group or an acid anhydride group, and an organic compound (B) having one hydroxyl group. A method for producing a biaxially oriented aromatic vinyl resin sheet, comprising: extruding from a T-die after melt-kneading with an extruder and biaxially stretching. 2. An organic compound (B) having one hydroxyl group.
Is a C1-C40 aliphatic alcohol, The manufacturing method of the biaxially-stretched aromatic vinyl resin sheet of Claim 1. 3. An organic compound (B) having one hydroxyl group.
Is an at least one alcohol selected from the group consisting of cetyl alcohol, stearyl alcohol and triethylene glycol monomethyl ether. 4. After melt-kneading, after extruding from a T-die, longitudinal stretching (uniaxial stretching step) is performed by a speed difference between rolls, and then transverse stretching (biaxial stretching step) by a tenter. 4. The method for producing a biaxially oriented aromatic vinyl resin sheet according to item 3. 5. The compounding amount of the organic compound (B) having one hydroxyl group is 0.1 to 100 parts by weight of the copolymer (A).
The method for producing a biaxially stretched aromatic vinyl resin sheet according to any one of claims 1 to 4, wherein the amount is 001 to 3 parts by weight. 6. A biaxial stretching temperature of (Tg-5) to (Tg +
20) ° C. [where Tg is the main dispersion temperature of the mixture (I). And the longitudinal stretching speed is 50 to 300% /
The method for producing a biaxially stretched aromatic vinyl resin sheet according to claim 4, wherein the transverse stretching speed is 2 to 80% / sec. 7. The copolymer (A) is styrene- (meth)
7. An acrylic acid copolymer according to claim 1, which is an acrylic acid copolymer.
The method for producing a biaxially stretched aromatic vinyl resin sheet according to the above item.