JP2002127240A - Method for manufacturing molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoforming method using a resin plate, low in molding proper temperature capable of shortening a molding cycle and good in moldability. SOLUTION: The resin plate is obtained from a styrenic resin composition which contains a continuous phase of a styrenic copolymer based on a styrenic monomer and a vinyl cyanide monomer and a dispersion phase of a graft copolymer obtained by the graft polymerization of the graft branch of the copolymer based on the monomer mixture system with a rubbery copolymer and is characterized in that Mw (weight average mol.wt.) of the styrenic copolymer of the continuous phase is 140,000-200,000 and a ratio (Mz/Mw) of Mz (average mol.wt.) is 3.0-10.0 and an Mw/Mn (number average mol.wt.) ratio is 2.0-3.0. This resin plate is heated to 110-170 deg.C to be subjected to blowing and stretched in a draw ratio of 2-7 times to be thermoformed to manufacture a thermoformed product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a molded article by heating a resin plate obtained by using a styrene resin composition having a specific molecular weight distribution at a specific temperature and thermoforming. In more detail, the resin plate manufactured by the extrusion molding method can be vacuum-formed and air-pressed at lower temperature,
The present invention relates to a processing method in which molding time is reduced.

[0002]

2. Description of the Related Art In general, thermoforming is a method in which a thermoplastic resin plate is heated and softened, an external force is applied to the plate while it is soft, and the plate is pressed against a required mold. This is a molding method that collectively includes vacuum molding in which a mold is closely adhered to the mold, and compressed air molding in which compressed air above atmospheric pressure or vacuum is used in combination.

[0003] More generally, when a resin plate manufactured by an extrusion molding method is used to form a desired shape by thermoforming, a molding material has a property of maintaining an appropriate viscosity for the molding method over a wide temperature range. Required.

For example, when an attempt is made to perform thermoforming using an ABS resin, it is necessary to appropriately increase the material viscosity as the draw ratio at the time of molding increases. In this case, it is conceivable to increase the melt viscosity by increasing the average molecular weight of the ABS resin itself. However, the viscosity at the time of stretching increases, and the processing temperature must be increased. As a result, the time for molding and processing is extended. You.

In order to improve the viscosity characteristics at the time of stretching, the ABS resin contains both an AS resin having a large average molecular weight and an AS resin having a small average molecular weight, or the molecular weight distribution of the AS resin is adjusted. Methods have been proposed, but again the molding temperature is high, the processing time is long,
It cannot be said that thermoforming in a short time by vacuum forming, pressure forming or the like is sufficient.

[0006] Furthermore, when the stretching ratio is large, it is desired that undesired thickness deviation does not occur in the molded product, and that the processing temperature is low and the processing time is short. In these molding methods, it is desired to easily obtain a desired melt viscosity according to the molding apparatus to be used, molding conditions, and the shape of the molded product.

Specifically, when a molded article such as an inner box of an electric refrigerator or a door liner is manufactured by blowing and pressure forming using a resin plate obtained by extrusion molding of an ABS resin, the stretching ratio is 2 to 7%. The following molding processability is required. Minimal deformation of the resin plate during heating Normally, the thermoforming of the inner box and door liner is performed by heating the resin plate → blowing by injecting air (air) → forced stretching with a plug → die transfer by vacuum suction and pressure air → cooling → It consists of the step of releasing the molded product. In this case, heating the resin plate (radiant heat)
When the deformation due to the weight of the resin increases, in extreme cases, contact with the device occurs, or the distance between the deformed portion and the heater becomes short, and the temperature distribution of the resin plate due to the radiant heat from the heater becomes extremely large. If the temperature of the resin plate becomes extremely high in the heating process, the high temperature portion of the resin plate is stretched in the next blowing process, and the portion becomes extremely thin or may burst. .

Further, in the next plug stretching step, the irregularities on the plug surface are transferred to the molded product. This is because the high temperature portion of the blown resin plate has a low material viscosity, so that the heated resin plate does not slip on the surface of the contacted plug and remains in contact until the next step. In some cases, the final step is completed in a state of poor appearance with the irregularities strongly transferred. In addition, if there is a temperature distribution in the portion that is stretched in the plug stretching process, the portion where the temperature is high and the viscosity is low is greatly stretched, and a thick portion and a thin portion are generated. The phenomenon occurs. At the same time, when a portion having a low temperature and a high viscosity is forcibly stretched at a higher speed by the plug, the orientation in the stretching direction remains stronger than other portions. In this case, when heat is subsequently applied, the orientation is relaxed, a thermal expansion / contraction phenomenon occurs, and the shape itself changes. In addition, the part with low viscosity and high viscosity cannot reproduce the unevenness of the mold even in the mold transfer process using vacuum and compressed air, and if the radius of curvature of the corners and ribs of the mold is small, follow Molding cannot be performed, and the radius of curvature of the portion of the molded product becomes large.

A wide molding temperature range. In particular, it is desired that good products can be obtained in a wide temperature range in which molding can be performed at a lower molding temperature. Since the glass transition temperature of the AS resin, which is a continuous phase of the ABS resin, is about 100 ° C.,
The temperature of the resin plate during molding is set so as to keep the temperature higher than this. It is desired that the molding can be performed while maintaining the molding temperature at a high temperature. However, as described above, the molding stability is reduced due to the high temperature. Desirably, the moldability is good on the low temperature side. This is because heat energy can be reduced and molding stability can be easily obtained. Further, the resin plate is heated to a glass transition point temperature of 100 ° C. or higher,
After the stretching process, the molded product is cooled to 100 ° C or less, and if the stretching process can be performed without any problem at a low temperature, the heating and cooling time is short, and the heating from the resin plate to the cooling of the molded product can be shortened. The time for the entire process can be shortened, and the productivity per unit time is improved.

[0010] The plug and the mold have slipperiness. If there is no slippage between the heated and blown resin plate and the plug, only the portion not in contact with the plug is drawn in the plug drawing step. If the contact surface between the plug and the heated and blown resin plate is large, the area that is not in contact with the plug will be small, and in this case, if there is no slip, only the small part that is not in contact with the plug will be stretched. The thickness of this portion is also reduced. Uneven thickness will be seen as a final product. Further, in the mold transfer step by vacuum / pressure air, which is the next step of plug stretching, if there is no slippage between the heated resin plate and the mold, only the portion not in contact with the mold will be stretched. . In the concave and convex portions of the mold, when the film is further stretched to follow the shape, if there is no slipperiness, a thin portion is observed on the inner surface of the concave portion. The thin portion has low strength and is easily deformed and cracked by external force.

Good transfer to a mold. The heated resin plate is not heated in the subsequent processing steps, but radiates heat in each step up to the cooling step, and the temperature of the resin plate decreases. Further, the stretching ratio also increases with each step. Among these, the step of transferring to the mold is the final stretching step, and it is required that the stretching and deformation can be sufficiently performed by vacuum and pressure and the transfer to the mold is good. If the mold transfer is insufficient, the radius of curvature of the corners and ribs of the mold will not be reproduced, and it will not be possible to insert or fit components in a later process.

Further, in recent years, the above-mentioned formability has been increasingly satisfied by increasing the size of the thermoformed product, complicating the shape, and reducing the thickness of the resin plate and shortening the molding cycle time for cost reduction. It has become difficult.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems by using a resin plate produced by an extrusion molding method, in which a molding method such as thermoforming, in particular, pressure molding is used. An object of the present invention is to provide a molding method in which the molding temperature is low and the molding cycle can be shortened when molding into a desired shape, and the moldability is good when molding into a desired shape.

[0014]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the continuous phase constituting the resin composition is extruded using a styrene resin composition having a specific molecular weight distribution. By heating the molded resin plate to a specific temperature, the molding cycle can be shortened, and it has been found that the moldability is good when a desired shape is obtained, and the present invention has been accomplished.

That is, the present invention comprises polymerizing a monomer mixture of a styrene monomer, a vinyl cyanide monomer and, if necessary, a vinyl monomer copolymerizable with these monomers. The styrene-based copolymer obtained by the continuous phase of the obtained styrene-based copolymer, the styrene-based monomer, the vinyl cyanide monomer, and the vinyl-based monomer copolymerizable with these monomers if necessary. Containing a dispersed phase of a graft copolymer obtained by graft polymerization of a graft branch of a copolymer comprising a monomer mixture of
Further, the weight average molecular weight (Mw) of the styrene copolymer in the continuous phase is 140,000 to 200,000, and the Z average molecular weight (M
z) and the ratio (Mz / Mw) of the weight average molecular weight (Mw) is 3.0 to 10.0, and the weight average molecular weight (Mw)
A resin plate obtained from a styrene resin composition having a ratio (Mw / Mn) of w) to a number average molecular weight (Mn) of 2.0 to 3.0 is heated to a temperature of 110 ° C to 170 ° C and blown. After that, it is stretched at a stretching ratio of 2 to 7 times, and thermoformed, which is a method for producing a molded article.

In a further preferred embodiment, a monomer mixture of a styrene monomer, a vinyl cyanide monomer and, if necessary, a vinyl monomer copolymerizable with these monomers is used. A continuous phase of a styrene copolymer (a) obtained by polymerization, and a styrene monomer, a vinyl cyanide monomer, and, if necessary, a copolymer with a rubbery polymer. The graft branches of a copolymer comprising a monomer mixture of possible vinyl monomers consist of a dispersed phase of a graft copolymer (b) obtained by graft polymerization, and this continuous phase of a styrene copolymer ( The weight average molecular weight of a) is from 140,000 to 17
100 parts by mass of styrene resin (A)
A polymer obtained by polymerizing a monomer mixture of a styrene monomer, a vinyl cyanide monomer, and a vinyl monomer copolymerizable with these monomers, if necessary, 60
By using a resin composition containing 0.1 to 3 parts by mass of a high-molecular-weight styrene-based polymer (B) having a weight-average molecular weight of 6.7 million or more in a styrene-based monomer unit in which the mass% or more is styrene-based monomer unit. is there.

More specifically, the styrene-based copolymer in the continuous phase is a styrene-acrylonitrile copolymer, and the graft copolymer in the dispersed phase is a rubber-like polymer of polybutadiene and / or styrene-butadiene copolymer. Styrene-based resins and styrene-based resin compositions, which are polymers obtained by graft-polymerizing a graft branch of a copolymer composed of a monomer mixture of styrene and acrylonitrile, can be used.

Further, in the present invention, the resin plate obtained by the extrusion molding method from the styrene resin composition is heated at a low temperature, blown, and then stretched to a stretching ratio of 2 to 7 times.
Another feature is that it can be thermoformed.

Hereinafter, the present invention will be described in detail. First, the styrene resin composition of the present invention will be described. The present invention relates to a styrene-based monomer, a vinyl cyanide-based monomer, and, if necessary, a styrene-based monomer obtained by polymerizing a monomer mixture of a vinyl-based monomer copolymerizable with these monomers. A monomer mixture of a continuous phase of a copolymer, a styrene-based monomer, a vinyl cyanide monomer, and optionally a vinyl-based monomer copolymerizable with these monomers in a rubber-like polymer. Contains a dispersed phase of a graft copolymer obtained by graft polymerization of a graft branch of a copolymer consisting of

The styrene monomer according to the present invention includes:
Styrene, α-methylstyrene, dimethylstyrene, vinyltoluene and the like can be mentioned, among which styrene is preferred. Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, fumaronitrile, and the like. Among these, acrylonitrile is preferable. These copolymerizable monomers used as needed include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, phenyl methacrylate, benzyl methacrylate, and the like. Methacrylate monomers such as isobornyl acrylate, acrylate monomers such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, maleic acid, itacone Acids, unsaturated dicarboxylic anhydride monomers such as citraconic anhydride, and imide compounds of unsaturated dicarboxylic acids such as maleimide, N-methylmaleimide, N-butylmaleimide, N-phenylmaleimide and N-cyclohexylmaleimide Include such mer, these vinyl monomers may be used alone or in combination of two or more.

The rubbery polymer used in the present invention includes butadiene-based polymers such as polybutadiene, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, polyisoprene, polychloroprene, propyl acrylate polymer, acrylic acid An acrylate polymer such as a butyl polymer, an ethylene-propylene-conjugated diene rubber, and the like can be given. These rubbery polymers can be used alone or in combination of two or more. Of these, polybutadiene and butadiene-styrene copolymer are preferred.

The method for producing the styrene copolymer is as follows:
Known methods such as an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method can be used. As the polymerization initiator and the chain transfer agent used at this time, the same types as those used when producing the following graft copolymer can be used.

As a method for producing the graft copolymer, known polymerization methods such as an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion-suspension polymerization method are used in combination with a batch system and / or a continuous system. Can be Among these, the method for producing the graft copolymer is preferably an emulsion polymerization method,
Using a latex-like rubber-like polymer, a monomer mixture of a styrene monomer and a vinyl cyanide monomer and, if necessary, a monomer copolymerizable therewith is polymerized by an emulsion polymerization method. Is preferred. However, in these production methods, it is difficult to obtain only the graft copolymer in which the graft branch is graft-polymerized to the rubber-like polymer described above, and it is a mixture with a styrene-based copolymer not grafted to the rubber-like polymer. Is common. Therefore, in the present invention, the polymer obtained by the above production method is referred to as a graft polymer (C), and when the graft copolymer is obtained alone, the graft copolymer and the graft polymer (C) are the same. And others are mixtures with the styrenic copolymers described above.

The composition ratio of the rubbery polymer and the monomer mixture in the above production method is selected in the range of 40 to 70% by mass of the monomer mixture in the presence of 30 to 60% by mass of the rubbery polymer. Is preferred. In this case, it is preferable that the volume average particle diameter of the rubbery polymer is usually selected in the range of 0.2 to 0.8 μm. In the case of the emulsion polymerization method, an emulsifier, a polymerization initiator,
The reaction is performed in a temperature range of 50 to 90 ° C. using a chain transfer agent. A known emulsifier can be used, and is not particularly limited. For example, anionic surfactants such as fatty acid salts, alkyl sulfate salts, alkyl benzene sulfonate salts, alkyl acid ester salts, alkyl diphenyl ether sulfonate salts, and polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters And nonionic surfactants such as glycerin fatty acid esters, and cationic surfactants such as alkylamine salts. These emulsifiers can be used alone or in combination.

The polymerization initiator may be a water-soluble or oil-soluble single type or a redox type.
An ordinary inorganic initiator such as a persulfate can be used alone, or can be used as a redox initiator in combination with a sulfite, a hydrogen sulfite, a thiosulfate, or the like. Further, t-butyl hydroperoxide, cumene hydroperoxide, benzoyl peroxide, organic peroxides such as lauroyl peroxide, azo compounds and the like may be used alone or in combination with sodium formaldehyde sulfoxylate or the like, and a redox initiator. Can also be used. The amount of these polymerization initiators is usually selected in the range of 0.1 to 5% by mass based on the monomer mixture.

Examples of the chain transfer agent include mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, terpinolene, and α-methylstyrene dimer.

The styrenic resin composition of the present invention comprises, as described above, a continuous phase of a styrenic copolymer such as a styrenic monomer and a monomer mixture of a rubbery polymer and a styrenic monomer. The copolymer contains a dispersed phase of a graft copolymer obtained by graft polymerization of a graft branch of the copolymer. Weight average molecular weight (Mw) of this continuous phase styrene copolymer
Is 140,000 to 200,000, and the ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is 3.0 to 1
0.0, and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2.0 to 3.0.
It is characterized by being. Preferably, the weight average molecular weight (Mw) of the styrene copolymer in the continuous phase is 150,000 to 180,000, and the Z average molecular weight (Mz) and the weight average molecular weight (Mw)
(Mz / Mw) is 3.2 to 5.0, and the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 2.2 to 2.8. Is preferred.

If a resin plate obtained from the continuous phase styrene copolymer having a weight average molecular weight (Mw) of less than 140,000 is used, the time until the sagging starts during heating is short, and the molding is started. By the way, the sag is large, and in an extreme case, the sagging resin plate comes into contact with the heater during heating or during movement to the molding process, which is not suitable for actual mass production. On the other hand, if it is larger than 200,000, it takes time to soften by heating, and it takes a long time to mold in the molding temperature range of the present invention, and the entire molding time is not shortened as in the prior art. Further, when Mz / Mw is less than 3.0 or exceeds 10, and Mw / Mn is 2.0
If it is less than 3.0 or more than 3.0, when molding is performed at the molding temperature of the present invention, an uneven thickness phenomenon occurs, and it is difficult to obtain a product having a uniform thickness.

Hereinafter, a resin composition comprising a styrene resin (A) and a high molecular weight styrene polymer (B), which is a preferred embodiment of the styrene resin composition, will be described in detail, but is not limited thereto. Not something. That is,
The styrene resin (A) is obtained by polymerizing a monomer mixture of a styrene monomer, a vinyl cyanide monomer, and, if necessary, a vinyl monomer copolymerizable with these monomers. Of styrene-based copolymer (a) obtained from styrene-based monomer, vinyl cyanide-based monomer and, if necessary, copolymerizable with rubber-like polymer The graft branch of a copolymer comprising a monomer mixture of various vinyl monomers comprises a dispersed phase of a graft copolymer (b) obtained by graft polymerization, and the continuous phase of the styrene copolymer (a ) Has a weight average molecular weight of 140,000 to 170,000, and the high molecular weight styrene polymer (B) is a styrene monomer,
A polymer obtained by polymerizing a monomer mixture of a vinyl cyanide monomer and, if necessary, a vinyl monomer copolymerizable with these monomers, and 60% by mass or more of styrene. It is a styrene-based polymer having a weight-average molecular weight of 6,700,000 or more as a monomer unit.

The content ratio of each component constituting the styrenic resin (A) of the present invention is such that the ratio of the styrenic copolymer (a) to the graft copolymer (b) is 50 to 85 by mass ratio.
It is preferably in the range of 50 to 15% by mass. When the ratio of the styrene copolymer (a) component to the graft copolymer (b) component is out of the above range, the impact resistance of the styrene resin composition containing the high molecular weight styrene polymer (B) is reduced. In addition, physical properties such as tensile strength are inferior, and moldability is inferior, so that an undesirable tendency appears. Also, if the proportion of the styrene copolymer (a) in the styrene resin composition is too large, the melt viscosity during thermoforming decreases, and deformation due to its own weight during heating of the resin plate tends to occur. There is. On the other hand, if the amount is too small, the melt viscosity increases, and it is necessary to raise the processing temperature and extend the molding cycle, and the mold transfer tends to be insufficient.

The styrenic copolymer (a) of the present invention
And the proportion of the styrene-based monomer, vinyl cyanide-based monomer and, if necessary, the monomer copolymerizable therewith in the graft copolymer (b) are 60 to 8 in terms of mass ratio.
It is preferably in the range of 0:15 to 45: 0 to 20 (however, the total of the monomers is 100% by mass).

The styrenic resin (A) includes a styrenic monomer, a vinyl cyanide monomer and, if necessary, a vinyl monomer copolymerizable with these monomers. And a continuous phase of a styrene-based copolymer (a) obtained by polymerizing a monomer mixture of a styrene-based monomer, a vinyl cyanide-based monomer, and The graft branch of a copolymer comprising a monomer mixture of a monomer and a vinyl monomer copolymerizable with the monomer comprises a dispersed phase of a graft copolymer (b) obtained by graft polymerization, and The weight average molecular weight of the styrene copolymer (a) is 140,000 to 170,000. If it is smaller than this range, the time until the resin plate is softened by heating is shortened, but the thermal deformation of the resin plate also becomes large, making the heating control difficult and not preferable. If the temperature exceeds this range, it takes time until the resin plate is softened by heating, and a long time is required for forming in the specific temperature range of the present invention, which is not preferable.
More preferably, the weight average molecular weight of the styrenic copolymer (a) is 150,000 to 160,000.

The styrenic copolymer (a) of the present invention can be obtained according to a known production method as described above for the styrenic copolymer. Specifically, a styrene-based monomer, a vinyl cyanide-based monomer, and, if necessary, other monomers copolymerizable therewith, are added to a polymerization initiator and, if necessary, a chain transfer agent. Examples of the method include those produced by an emulsion polymerization method, a suspension polymerization method, or a bulk polymerization method. Further, it may be a by-product at the time of producing the graft copolymer (b), or may be a separately produced styrene-based copolymer and a mixture thereof.

The method for producing the graft copolymer (b) can also be carried out by the method described above for the method for producing a graft copolymer.

Representative examples of the styrene resin (A) include ABS resin, MBS resin and AES resin.

Next, the high molecular weight styrene polymer (B) in the present invention will be described. The high-molecular-weight styrene polymer (B) is a monomer of a styrene monomer, a vinyl cyanide monomer, and, if necessary, a vinyl monomer copolymerizable with these monomers. A styrene-based polymer having a weight average molecular weight of 6.7 million or more, wherein the styrene-based monomer unit is 60% by mass or more.

Examples of the styrene monomer used include the above-mentioned styrene and the like, and among them, styrene is preferred. In addition, the vinyl cyanide-based monomer also includes the above-mentioned acrylonitrile, and among them, acrylonitrile is preferable. These copolymerizable monomers used as needed include methacrylate monomers such as methyl methacrylate, acrylate monomers such as methyl acrylate, and anhydrides such as maleic acid. Unsaturated dicarboxylic anhydride monomers such as, imide compound monomers of unsaturated dicarboxylic acids such as maleimide and the like, and these vinyl monomers,
They can be used alone or in combination of two or more.

The content of the styrene monomer unit in the high molecular weight styrene polymer (B) in the present invention is 60% by mass or more, preferably 65% by mass or more. When the content of the styrene-based monomer unit is less than 60% by mass, the dispersion of the high-molecular-weight styrene-based polymer (B) in the styrene-based resin (A) is reduced, and the appearance of a molded article is deteriorated.

In the high molecular weight styrenic polymer (B), when the content of the vinyl cyanide monomer and the vinyl monomer unit as other components exceeds 40% by mass, the high molecular weight styrenic polymer (B) ) In the styrene resin (A) is reduced, and the appearance of the molded article is deteriorated.

In order for the high molecular weight styrenic polymer (B) to have excellent thermoforming properties, it is essential that the molecular weight of the high molecular weight styrenic polymer (B) be extremely high. The weight-average molecular weight measured by gel permeation chromatography (GPC) is at least 6.7 million, preferably at least 7 million. If the weight average molecular weight is less than 6.70 million, the effect of imparting properties during thermoforming tends to be small. Further, the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) is preferably 2.7 or more. Since the molecular weight is extremely high, the compatibility is better when Mw / Mn is 2.7 or more. Particularly preferably, it is 3.0 to 15. Further, in order to obtain a predetermined molecular weight, the polymerization can be carried out by adjusting the amount of a chain transfer agent or catalyst used, the polymerization temperature, and the like during the polymerization described below.

The above-mentioned high molecular weight styrenic polymer (B)
A known method can be used as a method for obtaining the polymer. For example, examples of the polymerization method include emulsion polymerization, suspension polymerization, and solution polymerization. Among these, the application of the emulsion polymerization method is preferable. In the production method to which this emulsion polymerization method is applied, known emulsifiers can be used and are not particularly limited. For example, anionic surfactants such as fatty acid salts, alkyl sulfate salts, alkyl benzene sulfonate salts, alkyl acid ester salts, alkyl diphenyl ether sulfonate salts, and polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters And nonionic surfactants such as glycerin fatty acid esters, and cationic surfactants such as alkylamine salts. These emulsifiers can be used alone or in combination.

The polymerization initiator may be a water-soluble or oil-soluble single initiator or a redox initiator. For example, an ordinary inorganic initiator such as a persulfate may be used alone, or a sulfite may be used. , Bisulfite, thiosulfate and the like can be used as a redox initiator. Further, t-butyl hydroperoxide,
Organic peroxides such as cumene hydroperoxide, benzoyl peroxide and lauroyl peroxide, azo compounds and the like can be used alone or in combination with sodium formaldehyde sulfoxylate or the like and used as a redox initiator.

The method for recovering the high molecular weight styrene polymer (B) after polymerization used in the present invention is, for example, when it is obtained by emulsion polymerization, the obtained high molecular weight styrene polymer (B) The polymer is cooled to room temperature and acid-coagulated or salted out with an acid such as sulfuric acid, hydrochloric acid, phosphoric acid, or a salt such as aluminum chloride, calcium chloride, magnesium sulfate, aluminum sulfate, or calcium acetate. After precipitating the polymer, further filtration,
It can be obtained by washing and drying. Further, a known recovery method such as recovery of the obtained polymer latex by a technique such as spray drying or freeze drying can be used.

A preferred embodiment of the styrene resin composition is based on 100 parts by mass of the styrene resin (A).
60% by mass or more is a styrene-based monomer unit, and 0.1 to 3 parts by mass of a high-molecular-weight styrene-based polymer (B) composed of a styrene-based polymer having a weight-average molecular weight of 6.7 million or more. It is a resin composition. Further, 0.5 to 2 parts by mass of a high molecular weight styrene-based polymer (B) is added to 100 parts by mass of the styrene-based resin (A).

If the weight average molecular weight of the high molecular weight styrenic polymer (B) is smaller than 6,700,000, it is necessary to increase the addition amount. In this case, it takes time until the resin plate is softened by heating. In order to carry out molding in a specific temperature range, a long time is required, which is not preferable. Also,
If the amount is less than 0.1 part by mass, the effect of improving the viscosity of the styrene resin composition is small, the molding temperature is low, and the processing time is short, but rupture or knitting occurs during blowing, which is not preferable as a molded article. On the other hand, if the amount exceeds 3 parts by mass, the viscosity of the styrenic resin composition increases, the molding temperature rises, and the processing time becomes longer.

The styrene resin composition is prepared by (1) a method of weighing a predetermined amount of separately produced powdery, flake-like, bead-like, or pellet-like polymers and melt-mixing them. 2) A method of weighing a predetermined amount of each separately produced latex polymer, mixing and coagulating it to form a powder, (3) a graft polymer (C) and a high molecular weight styrene-based polymer (B). Is mixed and coagulated in a latex state to form a powder, and the styrene copolymer (a) is melt-mixed with the powder, (4) a high molecular weight styrene polymer (B) prepared in advance during graft polymerization Of latex,
Method for producing graft polymer (C), (5) high-molecular-weight styrene-based polymer (B) is prepared by first polymerizing high-molecular-weight styrene-based polymer (B) during graft polymerization, and then performing graft-polymerization. And a method for simultaneously producing the polymer and the graft polymer (C), but the method is not limited thereto.

The method of melt-mixing the components constituting the styrenic resin composition of the present invention is not particularly limited, and may be an extruder such as a single-screw extruder or a twin-screw extruder, or a Banbury mixer, a kneader / ruder. , Pressure kneader,
The resin composition can be melt-mixed using a general known processing device such as a kneader such as a heating roll.

The styrenic resin composition of the present invention contains a kind and amount of a lubricant, a releasing agent, a coloring agent, an antioxidant, an ultraviolet absorber, and a light-fastness which do not impair the properties of the resin composition of the present invention. Various resin additives such as agents, heat improvers, fillers, antistatic agents, flame retardants, antibacterial agents, fungicides, deodorants, etc. can be added as they are or in the form of master batches as needed. .

Next, the thermoforming method will be described. The extruded resin plate used for thermoforming is used in the form of a cut plate cut into a fixed size or a rolled plate. In the case of an apparatus configuration in which extrusion molding and thermoforming are linked, the extruded plate is supplied to the thermoforming machine in a softened state. After extrusion molding, the molded resin plate is sufficiently cooled to room temperature and then used for thermoforming. Although affected by the heating temperature at the time of thermoforming, it is considered that foaming may occur when the moisture absorption of the ABS resin plate exceeds 0.3%. For this reason, the extruded resin plate requires special care in storage after production. The humidity in Japan during the rainy season is high, and it is necessary to consider the storage environment according to the season. In some cases, it is possible to perform thermoforming without foaming by drying again and adjusting the amount of moisture absorption to an appropriate value.

The heating of the resin plate during thermoforming is an important issue for producing good molded products. Generally, a ceramic heater that emits long-wavelength far-infrared rays with high heating efficiency to plastic is used as a heat source. This is effective because a large number of rectangular areas are arranged, but local voltage adjustment and temperature adjustment can be performed. In some cases, a heater that emits short-wavelength near-infrared rays is used. Other heaters include a quartz tube heater, a mica heater, and a rod-shaped ceramic heater. These are arranged above and below the resin plate, and the heating of the resin plate portion is planned by voltage adjustment for each individual. In addition to the radiant heating described above, there are contact heating, hot air heating, and the like.

The relationship between the thickness of the resin plate and the heating is also an important issue for producing a molded product having a good relationship. When the resin plate is thin, the heating time is short, but when the heating is completed, the resin plate cools faster than when the resin plate is thick. For this reason, the heating temperature is set somewhat higher in consideration of the temperature that decreases after heating until the molding is completed. Alternatively, it is necessary to take measures such as shortening the time from heating to the start of molding. However, as the resin plate becomes thicker, characteristics such as thermal conductivity, infrared ray absorption coefficient, thermal expansion coefficient, and specific heat of the resin plate affect the heating conditions. In particular, from the thermal conductivity and the absorptivity of infrared rays, if the thickness of the resin plate increases, the temperature difference between the surface and the inner surface increases, and it takes time for the inside to reach an appropriate temperature.

The relationship between the hue of the resin plate and the heating is also an important issue for producing a molded article having a good relationship. In infrared heating, the deeper the color of the resin plate, the better the absorption of infrared light. When heating with the same heater, the time required for heating largely depends on the color density of the resin plate. For example, black absorbs infrared light better than white, and amber color absorbs infrared light better than amber color than yellow color. The difference in the infrared absorptance due to the lightness and darkness of the color decreases as the wavelength of the infrared light increases.

The relationship between the molding method and the heating is also an important issue for producing a molded article having a good relationship. In thermoforming, it is necessary that the resin plate maintain an appropriate molding temperature at the final stage of molding, for example, a temperature exceeding the glass transition temperature of the resin.
For this reason, the temperature at which the molding is started is determined in consideration of the temperature difference between the temperature of the resin plate at the time of starting the heating and the temperature from the end of the heating to the end of the molding.

An important issue for producing a molded product having good tolerance of a resin plate obtained by extrusion molding. If each resin plate has a large tolerance within the resin plate, it is difficult to obtain a molded product having the same thickness from each molded product under the same conditions. For this reason, except for a molded product having a small expansion ratio, by setting the tolerance of the resin plate used for thermoforming in an appropriate range, the thickness distribution of the obtained molded product is also in an appropriate range.

The thickness distribution of the obtained molded product clearly shows the superiority of the molded product. In general, a molded article is a good molded article in which the thickness of a specified specific portion is kept within a certain range. In this case, a method of adjusting the elongation of a specific portion by unevenly heating the resin plate is employed.
Further, in the case of uniform heating, the thickness distribution of the molded article is hardly constant. In this case, based on resin plates of the same thickness accuracy obtained from different resin raw materials, comparing the molded products obtained under the same molding conditions with uniform heating, the smaller the difference in the thickness of the specific portion is, the better the molding is. It can be said that it is a preferable resin for obtaining a product.

In the thermoforming, it is necessary to soften the resin plate with a pressing force of 100 kPa or less in vacuum forming and 500 kPa or less in pressure forming until the resin plate is sufficiently deformed. In the case of mass production, generally, the heating temperature of the resin plate is controlled at a characteristic portion by a value measured by an infrared sensor or a heating time. The state of the resin plate during heating is as follows. (1) When the resin plate whose outer periphery is clamped is heated, the surplus material that has expanded due to the heating has no place to go, causing a undulation phenomenon. (2) As the heating proceeds further, the undulation phenomenon becomes smaller and returns to the original flat plate. Since the resin is cooled and solidified while retaining the internal stress during the production of the resin plate, when heated to a temperature higher than the glass transition point of the resin, the stress is gradually released and contraction starts. When the amount of contraction becomes larger than the amount of expansion caused by heat, the resin plate returns to the original plate. (3) If heating is continued, the resin plate starts to sag. When the resin plate is softened to this state, molding becomes possible. As the softening of the resin plate progresses, the rigidity decreases rapidly, and the resin plate sags under its own weight. (4) If the heating is further continued, the resin plate foams or melts.

According to the present invention, the temperature range of the resin plate in the state immediately before the start of the molding described in (2) above is set to a specific value of a temperature of 110 ° C.
It is specified at ~ 170 ° C. As described above, thermoforming requires heating (softening), pressing (forming), and cooling (solidification) steps. If the heating temperature can be reduced, the temperature difference between the heating and cooling steps from room temperature is small, and the same apparatus is used. In this case, the time is reduced as compared with the case where the same resin plate is molded at a high heating temperature. As a result, the overall molding time is reduced and the number of productions at the same time is increased.

That is, the resin plate obtained from the above-mentioned styrene resin composition was heated to a temperature of 110 ° C. to 170 ° C., blown, and then stretched to a stretching ratio of 2 to 7 times.
Good molded products can be produced by thermoforming. When the temperature of the resin plate is less than 110 ° C., it is close to the glass transition temperature of the styrene-based copolymer in the continuous phase, the resin plate cannot be softened by heating, the blowing after heating becomes insufficient, and the The shape is not stretched. On the other hand, if the temperature exceeds 170 ° C., the resin plate is excessively softened by heating, the resin plate is stretched too much by blowing, and wrinkles are generated in the molded product during molding. Further, in an extreme case, the resin plate is ruptured by blowing after heating. On the other hand, if the stretching ratio is less than 2 times, a sufficient thickness uniformity can be obtained by molding in a simple process such as vacuum molding and pressure molding without actually performing the blowing step. If it exceeds 7 times, the expansion ratio is large, the thickness of the molded product is small with respect to the thickness of the original resin plate, and the thickness is increased by a series of steps of blowing → drawing by plug → die transfer by vacuum and pressure. Cannot be maintained in practice.

When these styrenic resin compositions are used, preferably, the heating temperature of the extruded resin plate is 115-115.
It is in the range of 165 ° C, particularly preferably 120 to
160 ° C. range. Furthermore, the present invention can be carried out at less than 130 ° C., which was conventionally difficult to thermoform using the styrene-based resin composition described above, and the low-temperature heating temperature of the resin plate is preferably 120 ° C. or more and less than 130 ° C. Another feature of the present invention is that the thermoforming can be performed.

A molding machine for performing thermoforming of the present invention, a heating method,
The apparatus such as a mold is not particularly limited, and a molding machine such as a vacuum molding machine and a compressed air molding machine, a heating method such as an electric heater, a far-infrared heater, and a near-infrared heater, a heater shape such as a short shape and a rod shape, and the like. A molded product can be manufactured by thermoforming with a general known device. Particularly suitable for use in the inner box of an electric refrigerator.

[0061]

The present invention will be described in detail with reference to the following examples and comparative examples, but the present invention is not limited to the following examples. All parts and percentages in the examples and comparative examples are based on mass unless otherwise specified. Further, each physical property in each example and comparative example was evaluated and measured by the following methods.

Next, the styrene resin composition will be described. (1) Production Example of Styrene-Based Copolymer (a-1): 30 parts of styrene, 30 parts of acrylonitrile, 30 parts of acrylonitrile were placed in a stainless steel autoclave equipped with a stirrer, a heating / cooling device, a thermometer, and a device for adding raw materials and auxiliaries. 0.07 parts of calcium phosphate, n-dodecyl mercaptan 0.
65 parts and 100 parts of deionized water were charged, and the inside of the polymerization system was replaced with nitrogen gas. Under stirring, the internal temperature was raised to 96 ° C., and 0.01 part of potassium persulfate was added to initiate a polymerization reaction. Immediately after the initiation of the polymerization, 40 parts of styrene were continuously added at a constant rate over a period of 7 hours.
Hold for 30 minutes, then raise the temperature to 105 ° C over 30 minutes,
Maintained for 1.5 hours. The temperature was raised to 115 ° C. over a further 30 minutes and maintained for 3 hours to complete the polymerization. Then cool down,
The resultant was filtered, washed with water, and dried to obtain a beaded styrene-based copolymer (a-1). The weight average molecular weight of this polymer is 1
It was 550,000.

(A-2): In the reaction vessel used in (a-1), 60 parts of styrene, 40 parts of acrylonitrile, 4 parts of calcium tertiary phosphate, 0.1 part of t-dodecyl mercaptan.
15 parts and 57 parts of deionized water were charged, and the inside of the polymerization system was replaced with nitrogen gas. Under stirring, the internal temperature was raised to 95 ° C., and 0.05 part of t-butyl-peroxy 3,5,5-trimethylhexanate was added to initiate a polymerization reaction. Immediately after starting the polymerization, 33 parts of styrene, 64 parts of deionized water,
While continuously adding 0.35 parts of potassium peroxide over 6.5 hours, the temperature was maintained at 95 ° C for 4 hours, further maintained at 105 ° C for 2 hours, and subsequently maintained at 115 ° C for 3.5 hours to complete the polymerization. . Thereafter, the mixture was cooled, filtered, washed with water, and dried to obtain a beaded styrene-based copolymer (a-2). The polymerization average molecular weight of this polymer was 215,000.

(2) Production Example of Graft Polymer Production of Rubbery Polymer After replacing the butadiene 100 in a stainless steel autoclave equipped with a stirrer, a heating / cooling device, a thermometer, a pressure gauge, and a device for adding raw materials and auxiliaries, Part, potassium rosinate 2.5
, 0.4 parts of t-dodecylmercaptan, 1.5 parts of potassium carbonate, and 100 parts of deionized water, and the internal temperature was raised to 50 ° C under stirring. When the internal temperature reached 50 ° C., 0.5 part of potassium persulfate was added. An exotherm occurred a few minutes later, confirming the start of polymerization. Internal pressure is 9.8 × 10 ⁴ P
The polymerization was terminated at the time point of a, and cooled. The solid content concentration of the obtained rubbery polymer latex was 50%, and the average particle size of the rubbery polymer was 0.31 μm.

Production of Graft Polymer In a stainless steel autoclave equipped with a stirrer, a heating / cooling device, a thermometer, and a device for adding raw materials and auxiliaries, 200 parts of a rubbery polymer latex obtained by
Parts) and deionized water (including water in latex) 366
Then, the inside of the polymerization system was replaced with nitrogen gas, and the internal temperature was raised to 60 ° C. under stirring. When the internal temperature reached 58 ° C. on the way, 13 parts of deionized water contained 0.005 ferrous sulfate heptahydrate.
Parts, ethylenediaminetetraacetic acid tetrasodium dihydrate 0.0
A solution consisting of 1 part and 0.3 part of formaldehyde / sodium bisulfite dihydrate was added. When the internal temperature reached 60 ° C., 70 parts of styrene, 30 parts of acrylonitrile,
2,4-diphenyl-4-methyl-1-pentene 0.1
Parts of a monomer mixture and 27 parts of deionized water, 1.5 parts of a higher fatty acid soap, and a solution consisting of 0.4 parts of diisopropylbenzene hydroperoxide were continuously added.
It finished in 6 hours. Thereafter, the reaction was continued at a temperature of 70 ° C. for 2 hours, and then the internal temperature was cooled. The solid content of the obtained graft polymer latex was 33.0%. An antioxidant (1.5 parts) was added to the obtained mixed latex, and the latex was added to an aqueous magnesium sulfate solution heated to a temperature of 95 ° C. to coagulate, filtered, washed and dried to obtain a white powdery resin composition. I got This graft polymer is designated as C. The graft ratio of the graft polymer C was 85.1.
%, And the weight average molecular weight of the ungrafted copolymer is 17.
It was 50,000. Therefore, this graft polymer C is
It consists of a graft copolymer (b) and a non-styrene copolymer.

(3) High molecular weight styrene-based polymer (B) B-1: 71 parts of styrene, 24 parts of acrylonitrile were placed in a stainless steel autoclave equipped with a stirrer, a heating / cooling device, a thermometer, and a device for adding raw materials and auxiliaries. Higher fatty acid soap 2
0 parts and 2,000 parts of deionized water were charged, the inside of the polymerization system was replaced with nitrogen gas, and the temperature was raised to an internal temperature of 40 ° C. with stirring. When the internal temperature reached 40 ° C., 0.005 part of ferrous sulfate heptahydrate, 0.01 part of ethylenediaminetetraacetic acid tetrasodium dihydrate, 0.01 part of formaldehyde / sodium bisulfite dihydrate in 26 parts of deionized water Add a solution consisting of 0.3 parts, and keep the internal temperature 40
C. and maintained in t-butyl hydroperoxide 0.00
While continuously dropping 6 parts, the mixture was heated and stirred for 4 hours and 30 minutes to carry out polymerization. Further, 5 parts of styrene and 0.1 part of diisopropylbenzene hydroperoxide were continuously added over 30 minutes. After the addition was completed, the temperature was raised to 70 ° C., the reaction was continued for another 2 hours, and the reaction was terminated by cooling. An aqueous magnesium sulfate solution was added to the obtained latex for coagulation, followed by filtration, washing and drying to obtain a high molecular weight styrene-based polymer (B-1). The weight average molecular weight of this polymer is 70
Mw / Mn was 10.2.

B-2: 2.0 parts of a higher fatty acid soap and 80 parts of deionized water were charged into the reaction vessel used in B-1, and the inside of the polymerization system was replaced with nitrogen gas. The temperature rose. When the internal temperature reached 70 ° C, 26 parts of deionized water contained 0.005 part of ferrous sulfate heptahydrate, 0.01 part of tetrasodium ethylenediaminetetraacetate dihydrate, 0.01 part of formaldehyde.
A solution consisting of 0.3 parts of sodium bisulfite dihydrate was added, and the mixture was stirred for 4 hours and 30 minutes while continuously adding 70 parts of styrene, 30 parts of acrylonitrile and 0.1 part of potassium persulfate while maintaining the internal temperature at 70 ° C. Then, polymerization was carried out, and the reaction was terminated by cooling. An aqueous magnesium sulfate solution was added to the obtained latex for coagulation, followed by filtration, washing and drying to obtain a styrene polymer B-2. The weight average molecular weight of this polymer was 1.7 million, and Mw / Mn was 8.5.

The physical properties of the polymer of each component constituting the styrenic resin composition were measured by the following methods. (1) Weight average molecular weight (a) Styrene-based copolymer (a-1), (a-2), ungrafted copolymer in graft copolymer (C), and high-molecular-weight styrene-based polymer (B ) Has a weight average molecular weight of
Gel permeation chromatography (GP
C) The molecular weight was measured using an apparatus under the following conditions, and the molecular weight is in terms of polystyrene. (B) Gel permeation chromatograph (GP
C) Measurement conditions of the apparatus: "SYSTEM-21" column, manufactured by Tosoh Corporation; PLgel MIXED-B temperature; 40 ° C solvent; tetrahydrofuran detection; RI concentration; 0.2% injection amount; 100 μl calibration curve; standard polystyrene (Made by Polymer Laboratories)
Compliant with.

(C) Conditions for Pretreatment of Styrene Copolymer in Continuous Phase of Styrene Resin Composition A sample of about 1.2 × 10 ⁻³ kg of a styrene resin composition was charged to 1
Transfer to a 00 ml Erlenmeyer flask and add methyl ethyl ketone (M
EK) After adding 30 × 10 ⁻³ kg, the mixture was heated at 23 ° C. for 24 hours.
After stirring for an hour, the insoluble matter in MEK was separated by a centrifuge, and the mixture was allowed to stand for 30 minutes after the centrifugation operation. The operating conditions of this centrifuge were set as follows. Temperature: -9 ° C Rotational speed: 20,000 rpm Time: 60 minutes The supernatant obtained by this centrifugation operation was put into a 300 ml beaker containing 150 ml of methanol to precipitate, and the precipitate was suction-filtered using filter paper. I do. The filtrate was dried with a vacuum dryer at a temperature of 23 ° C. for 24 hours. The obtained sample was used as a GPC measurement sample as a styrene-based copolymer in a continuous phase of a styrene-based resin composition.

(D) Pretreatment method for measuring the molecular weight of the non-styrene-based copolymer in the graft polymer (C) About 20 × 10 ⁻³ kg of a latex of the graft polymer (C) was precipitated with 100 ml of methanol. The solidified product is subjected to suction filtration using a filter paper. The filtrate is dried in a vacuum dryer for 24 hours at room temperature. About 1.2 × 10 of the obtained sample
^-3 kg in a 100 ml Erlenmeyer flask, and 30 × 10 ^-3 kg of methyl ethyl ketone (MEK) was added.
The mixture was stirred at 3 ° C. for 24 hours, and then the insoluble matter in MEK was separated by a centrifuge, and the mixture was allowed to stand for 30 minutes after the centrifugation operation. The operating conditions of this centrifuge were set as follows. Temperature: -9 ° C Rotation speed: 20,000 rpm Time: 60 minutes The supernatant and the precipitate separated by centrifugation are separated, and the obtained supernatant is put in 150 ml of methanol.
The precipitate is placed in a 0 ml beaker, and the precipitate is suction-filtered using a filter paper. The filtrate is dried in a vacuum dryer at room temperature for 24 hours. The obtained sample was used as a GPC measurement sample.

(2) Method for measuring volume average particle diameter of rubbery polymer in rubbery polymer latex The particle size distribution of the rubbery polymer of the present invention was determined by a laser diffraction scattering method. The measurement conditions are as follows. Apparatus: COULTER LS 230 (COULTER LS 230)
Concentration: 2.0% Diluent solvent: distilled water Analysis software: Version 2.05

(3) Method of Measuring Graft Ratio The precipitate obtained by centrifugation when measuring the weight average molecular weight was dried with a vacuum dryer to obtain an insoluble matter X. Further, the mass Y of the acrylonitrile monomer quantified by the Kjeldahl nitrogen method using the sample of this insoluble matter and the mass Z of the styrene monomer quantified by pyrolysis gas chromatography were determined, and the graft ratio (%) = 100 × (Y + Z)
/ {X- (Y + Z)}.

Examples 1 to 3 and Comparative Examples 1 to 4 The styrenic copolymers (a-1) and (a-
2) The graft polymer C and the high-molecular-weight styrene-based polymer (B) were kneaded at a mass ratio shown in Tables 1 and 2 by a twin-screw extruder and pelletized.

Using the pellets, a resin plate was molded by an extruder, and the thermoformability of the resin plate was evaluated by the following method. Table 1 shows the results. (1) Resin plate molding Using a styrene-based resin composition and a white colored masterbatch containing titanium oxide, an extruder with a T-die (SHT-90 manufactured by Hitachi Zosen Corporation) and a thickness of 1. A resin plate of 5 mm was manufactured, and 400 ×
A 400 mm resin plate was cut out, and the thickness of each of the cut out resin plates was measured by a micrometer at a thickness of 7 points (total of 24 points) every 5 cm in the vertical and horizontal directions. In addition, four color values, which are intersections of parallel lines separated by 10 cm from the vertical and horizontal center lines, were measured by a color difference meter (# 80 manufactured by Nippon Denshoku Industries Co., Ltd.). As a result, the thickness tolerance is within 1.0%, and the color value at each measurement point is L
= 92.87, a = -1.42, and b = -0.73.

(2) Thermoforming Next, a compressed air / vacuum forming machine (FK-
0431-10). The specifications of the compressed air / vacuum forming machine subjected to thermoforming were fixed as follows. Heater: Double-sided radiant heating Heater element: Far-infrared quick response heater (16 each for upper and lower) Heater control: Addition rate control per unit Heating control: Resin plate temperature remote measurement control Vacuum pump Model: RV-21 Rotary vane type Motor: 3.7 kW Displacement: 2,000 l / min. For the temperature of the resin plate after heating the heater, observe the resin plate surface temperature distribution with Thermoviewer JTG-6300 manufactured by JEOL Ltd. and control the temperature of each heater so that the surface temperature immediately before blow molding becomes uniform. went.

The mold A has a size of 270 mm and a depth of 150 mm.
R of the four ridges in the depth direction is 1.0 mm,
The R at the corners of the other portions is 10.0 mm.
In this mold, the draw ratio is about 3 times. The shape of the plug used for molding with this mold was 225 mm per piece, height 14 mm.
At 0 mm, R at each corner is 10 mm. Also on the surface,
White flannel fabric is evenly applied. Mold B is 150 on one side
mm, 150mm depth box type, 4 ridges R in the depth direction
Is 1.0 mm, and the R at the corners of the other portions are all 8.0 mm. In this mold, the draw ratio is about 5 times. The shape of the plug used for molding with this mold is
R is 43 mm, height is 137.5 mm, and R of each corner is 8 mm. The surface is evenly coated with white flannel fabric.

The molding step was performed as follows. The resin plate was heated to a predetermined temperature, and after one second from the end of the heating, blowing was started. Blowing was performed for 2 seconds using compressed air of 198 kPa. The descent of the plug indicates the end of heating 5.5.
Started in seconds. Vacuum forming and pressure forming start 7 seconds after heating and 7.5 seconds after heating, respectively, and the degree of vacuum is -97 kPa,
The pressure was maintained at 98 kPa for 20 seconds.

1) Uneven thickness ratio: The obtained molded product was cut vertically from the center of one side of the opening to the center of the bottom, and the minimum thickness A at the cut surface was measured. Ratio (B
/ A) was expressed as the thickness deviation ratio. The smaller the thickness deviation ratio, the smaller the thickness deviation, which is preferable. 2) Radius of curvature: The measured value of the radius of curvature R in a direction parallel to the opening centered on a point at an intermediate depth from the opening to the bottom of the four ridges of the molded article was shown. Since the radius R value of the part of the molds A and B is 1.0 mm, the closer the curvature radius R value of the part is to 1.0, the better the mold transferability.

[0079]

[Table 1]

[0080]

[Table 2]

From Tables 1 and 2, the following becomes clear. By using the styrenic resin composition according to the present invention, a molding temperature range suitable for thermoforming is wide even on a low temperature side, and there is little uneven thickness, and a molded article having good mold transferability can be obtained (Example 1). ~ 2). This effect is obtained even when the stretching ratio is high (Example 3). On the other hand, the styrene resin composition of the comparative example that does not satisfy the essential requirements of the present invention,
The knitted meat is large (Comparative Examples 1, 3, and 4), the mold transferability is inferior (Comparative Example 2), and the moldability range is only on the high temperature side, and a good molded product cannot be obtained.

[0082]

According to the present invention, when a resin plate obtained from the styrene resin composition having a specific molecular weight distribution of the present invention is molded into a target shape by a molding method such as thermoforming, an appropriate temperature range for molding is determined. Since the molding can be performed at a wide temperature even at a low temperature, the molding cycle can be shortened. Further, when molding into a desired shape, the uneven thickness is small and the effect of excellent mold transferability is exhibited, and the industrial value is extremely large.

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Claims (5)

[Claims] 1. A resin plate obtained from the following styrene resin composition is heated to a temperature of 110 ° C. to 170 ° C., blown, stretched to a stretching ratio of 2 to 7 times, and thermoformed. Manufacturing method of molded products. Styrene resin composition, styrene monomer, vinyl cyanide monomer,
And a styrene-based copolymer continuous phase obtained by polymerizing a monomer mixture of these monomers and a copolymerizable vinyl monomer, if necessary, and a styrene-based monomer in the rubber-like polymer. Of a copolymer of a monomer, a vinyl cyanide monomer, and, if necessary, a graft mixture of a copolymer comprising a monomer mixture of vinyl monomers copolymerizable with these monomers. A styrene copolymer containing a dispersed phase and having a weight average molecular weight (Mw) of 140,000 to 2
0,000, the ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is 3.0 to 10.0, and further, the weight average molecular weight (Mw) and the number average molecular weight (Mw).
a resin composition having a ratio (Mw / Mn) to n) of from 2.0 to 3.0. 2. A styrene-based resin composition comprising 0.1 to 3 parts by mass of a high-molecular-weight styrene-based polymer (B) per 100 parts by mass of the following styrene-based resin (A). The method for producing a molded article according to claim 1, wherein The styrene resin (A) is obtained by polymerizing a monomer mixture of a styrene monomer, a vinyl cyanide monomer, and, if necessary, a vinyl monomer copolymerizable with these monomers. Of styrene-based copolymer (a) obtained from styrene-based monomer, vinyl cyanide-based monomer and, if necessary, copolymerizable with rubber-like polymer The graft branch of a copolymer comprising a monomer mixture of various vinyl monomers comprises a dispersed phase of a graft copolymer (b) obtained by graft polymerization, and the continuous phase of the styrene copolymer (a ) Has a weight average molecular weight of 140,000 to 170,000, and the high molecular weight styrene-based polymer (B) contains a styrene-based monomer, a vinyl cyanide-based monomer, and if necessary, these monomers. Obtained by polymerizing a monomer mixture with a copolymerizable vinyl monomer Coalescence, styrenic polymer 60 mass% or more is in the styrene monomer units and a weight average molecular weight of 6.7 million or more. 3. The styrene-based copolymer is a styrene-acrylonitrile copolymer, and the graft copolymer of the dispersed phase is a rubber-like polymer of polybutadiene and / or butadiene-styrene copolymer. The method for producing a molded article according to claim 1, wherein the graft branch of the copolymer comprising the polymer mixture is a polymer obtained by graft polymerization. 4. A resin plate obtained by extrusion molding using a styrene-based resin composition is heated at a temperature of from 120 ° C. to less than 130 ° C., blown, stretched to a stretching ratio of 2 to 7 times, and thermoformed. The method for producing a molded article according to claim 1, wherein: 5. A molded article obtained by the production method according to claim 1.