JP2000025091A - Manufacture of thermoplastic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thermoplastic resin sheet to obtain the resin sheet having excellent moldability, heat resistance and oil resistance and a thermoplastic resin foam sheet. SOLUTION: The method for manufacturing a thermoplastic resin sheet comprises the steps of setting an L/D ratio of piping for coupling an extruder exit to a molding die to 25 or more in the case of melt kneading a resin composition containing (A) 40 to 98 wt.% of a styrene resin and (B) 60 to 2 wt.% of a crystalline thermoplastic resin having a melting temperature specified according to JIS K 7121 of 100 to 300 deg.C by an extruder and extrusion foam molding the composition, and regulating a flow rate of the composition in the piping to 100 to 50,000 g/min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin sheet capable of obtaining a sheet suitable as a material for producing food containers such as prepared dishes, and a method for producing a thermoplastic resin foam sheet.

[0002]

2. Description of the Related Art Styrene resins are widely used as container materials for various foods such as side dishes because of their excellent moldability and rigidity. However, since the styrene-based resin has poor heat resistance, there is a problem that the container is deformed when the food and the like are heated together with the food container in a microwave oven. Such a problem of deformation due to heating tends to be particularly pronounced in foods containing a large amount of edible oil.

[0003] As a method of solving such a problem,
There is known a method of coating the surface of a container made of a styrene resin with a heat-resistant resin sheet. However, such a method complicates the manufacturing process and increases the manufacturing cost,
There is room for improvement.

There is also a method of forming a sheet obtained by extruding a mixture of a styrene-based resin and a heat-resistant resin to obtain a container. However, when the heat-resistant resin is simply mixed, the heat resistance is improved. There is a problem that the appearance of the product is deteriorated due to a decrease in the moldability and an unevenness on the surface. Furthermore, in the usual extrusion molding using an extruder, the obtained sheet has a so-called sea-island structure (for example, the average particle diameter of the island is about 0.01 to 10 μm), so that formability, rigidity, heat resistance, and oil resistance are obtained. It is difficult to obtain a sheet having all of them in a well-balanced manner.

An object of the present invention is to provide a method for producing a thermoplastic resin sheet capable of obtaining a resin sheet having excellent moldability, heat resistance and oil resistance, and a thermoplastic resin foam sheet.

[0006]

The present inventor has paid attention to the fact that the problem of the sea-island structure can be solved by making the phase structure a bicontinuous phase structure. As a result of repeated studies to obtain, the L / D ratio of the pipe from the extruder outlet to the molding die and the flow rate of the raw material in the pipe are related, and by setting them to the optimum range,
It has been found that the above object can be achieved.

The present invention relates to (A) a styrenic resin 40 to 9
Extrusion molding is performed by melt-kneading a resin composition containing 8% by weight and (B) 60 to 2% by weight of a crystalline thermoplastic resin having a melting temperature in the range of 100 to 300 ° C specified in JIS K7121 by an extruder. In doing so, the L / D ratio of the pipe connecting the outlet of the extruder and the molding die is set to 25 or more, and the flow rate of the resin composition in the pipe is set to 100 to 50,000 g /.
The present invention provides a method for producing a thermoplastic resin sheet, characterized in that the method is adjusted to a minute.

The present invention also relates to (A) a styrene resin 40
A resin composition containing from about 98% by weight to about 98% by weight and (B) 60 to 2% by weight of a crystalline thermoplastic resin having a melting temperature in the range of 100 to 300 ° C specified by JIS K7121 is melt-kneaded by an extruder and extruded. When performing foam molding, the L / D ratio of the pipe connecting the extruder outlet and the molding die is set to 25 or more, and the flow rate of the resin composition in the pipe is set to 100 to 50.
Provided is a method for producing a thermoplastic resin foam sheet, which is adjusted to 000 g / min.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The resin composition used in the method for producing a thermoplastic resin sheet of the present invention contains a styrene resin as the component (A) and a crystalline thermoplastic resin as the component (B). .

Examples of the styrene resin as the component (A) include a polymer of a styrene monomer and a copolymer of a styrene monomer and another monomer copolymerizable therewith.

As the styrene monomer, styrene,
Alkyl-substituted styrene such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 4-t-butylstyrene, 2,4-dimethylstyrene, α-methylstyrene, α-methyl-4- One or more selected from α-alkyl-substituted styrene such as methylstyrene, halogenated styrene such as 2-chlorostyrene and 4-chlorostyrene, and the like can be given.

Other monomers copolymerizable with the styrene monomer include acrylic acid or methacrylic acid, methyl acrylate or methyl methacrylate, ethyl acrylate or ethyl methacrylate, butyl acrylate or butyl methacrylate, acrylic acid 2 Acrylic acid such as -ethylhexyl or 2-ethylhexyl methacrylate (C _1-
C ₈₎ esters or methacrylic acid (C ₁ ~C ₈₎ esters, acrylonitrile, maleic anhydride, maleimide,
One or more types selected from maleic acid or derivatives thereof such as N-substituted maleimide such as N-methylmaleimide and N-ethylmaleimide can be mentioned.

The styrene resin as the component (A) may be a rubber-modified styrene resin. Examples of the rubber used in the production of the rubber-modified styrene resin include non-styrene rubbers such as butadiene rubber, butadiene-isoprene rubber, butadiene-acrylonitrile rubber, ethylene-propylene rubber, isoprene rubber, acrylic rubber, and ethylene-vinyl acetate rubber; At least one selected from styrene rubbers such as butadiene rubber and styrene-isoprene rubber can be used. The butadiene rubber may be a high cis type having a high content of cis-1,4 structure or a low cis type having a low content of cis-1,4 structure. When the rubber-modified styrenic resin is used, the content of the rubber component in the resin is 1 to 2
It is preferably 0% by weight.

The polymerization form when the component (A) is made into a copolymer is not particularly limited, and may be a block copolymer,
It may be a random copolymer or a copolymer having a tapered block structure.

The content of the component (A) in the resin composition is from 40 to 98% by weight, preferably from 60 to 85% by weight.

[0016] The crystalline thermoplastic resin of the component (B) is JI
The melting temperature specified by SK7121 is 100 to 300
° C, preferably 120 to 230 ° C, particularly preferably 15 ° C.
It is in the range of 0 to 200 ° C. Melting temperature is 10
When the temperature is 0 ° C or higher, sufficient heat resistance can be imparted,
When the temperature is 300 ° C. or lower, the moldability is good, so that the sheet appearance becomes good and the impact resistance is also increased.

As the crystalline thermoplastic resin as the component (B), olefinic resins (polypropylene, polypropylene having a sharp molecular weight distribution obtained using a metallocene catalyst, etc., ethylene-propylene copolymer, polymethylpentene, etc.); Crystalline polystyrene (isotactic or syndiotactic), polyster-based resin (polyalkylene terephthalate such as polyethylene terephthalate and polybutylene terephthalate, polyalkylene naphthalate such as polyethylene naphthalate and polybutylene naphthalate, alkylene terephthalate or alkylene naphthalate) A polyester copolymer containing a unit of 50 mol% or more, preferably 70 mol% or more), a polyamide resin (trade name: nylon 6, nylon 66, nylon 1)
0, Nylon 12, Nylon 610, Nylon 612, etc. homo- or copolymer, aromatic polyamide, etc., polycarbonate resin (bisphenol A type polycarbonate, etc.), polysulfone resin (polysulfone, polyether sulfone, etc.), polyphenylene ether type One or more selected from a resin, a polyphenylene sulfide resin, a polyether ether ketone resin, a polyacetal resin, a thermoplastic elastomer (a thermoplastic polyurethane elastomer, a polyester elastomer, and the like) can be given. As the component (B), among these, an olefin resin, particularly, polypropylene is preferable.

The content of the component (B) in the resin composition is 60 to 2% by weight, preferably 40 to 15% by weight.

The resin composition may further contain, if necessary, a compatibilizer, a coloring agent such as a pigment, a dispersant such as a higher fatty acid salt, an inorganic filler such as talc, a conductivity-imparting agent, an antistatic agent, and a silicone. Can be added.

In the method for producing a thermoplastic resin sheet and a thermoplastic resin foam sheet of the present invention, when the resin composition melt-kneaded by an extruder is subjected to extrusion molding or foam extrusion molding, an extruder outlet and a molding die are connected. L / D of connecting pipe
The ratio is set to 25 or more, and the flow rate of the resin composition in the pipe is adjusted to 100 to 50,000 g / min.

Examples of the foam molding method include a method in which a chemical foaming agent is added to perform extrusion molding, a method in which foaming gas raw material is extruded while being injected, and a method in which a liquid foaming gas raw material is impregnated in a resin composition. Can be applied. Examples of the chemical foaming agent and foam gas raw material include hydrocarbons such as sodium hydrogen carbonate, ammonium hydrogen carbonate, azodicarbonamide, azobisisobutyronitrile, liquid propane, and butane.

The L / D ratio of the pipe is 25 or more,
It is preferably at least 30 and particularly preferably at least 40. When the L / D ratio is 25 or more, the obtained resin sheet and resin foam sheet can have a bicontinuous phase structure.

The "pipe" in the present invention may be a single pipe or a plurality of pipes connected by a suitable adapter. The cross-sectional shape in the width direction is not limited. , An ellipse, a quadrangle or more polygon, or the like. When there are a plurality of pipes, each pipe (including an adapter when the adapter substantially forms a pipe)
L / D ratio is calculated for each of them, and their total value is defined as the L / D ratio in the present invention. When the cross-sectional shape is other than circular, the D (diameter) value is obtained by converting into a circle having an equivalent area. The magnitude of the absolute value of the D value (the magnitude of the diameter) is appropriately determined within a range where a predetermined flow rate of the resin composition can be secured.

The flow rate of the resin composition in the pipe is 100
~ 50,000 g / min, preferably 400-300 g / min.
00 g / min, particularly preferably 500 to 10000 g / min.
Minutes.

The thermoplastic resin sheet and the thermoplastic resin foam sheet obtained by the production method of the present invention have a bicontinuous phase structure. The “bicontinuous phase structure” refers to the MD direction (sheet flow direction) and TD of the resin sheet (or resin foam sheet).
In either direction (the direction orthogonal to the MD direction), the styrene resin phase of the component (A) and the thermoplastic resin phase of the component (B) exist in a state independent of each other, such as particles or fibrous forms. This does not mean that both phases form a mixed phase structure in a state where they are connected to each other in a network. By adopting such a bicontinuous structure, unlike the sea-island structure, the component (A) and the component (B)
The properties inherent in each of the components can be sufficiently exhibited.

Further, the thermoplastic resin sheet and the thermoplastic resin foam sheet obtained by the production method of the present invention particularly have a volume change rate represented by the following formula (I) and a weight represented by the following formula (II). It is preferable to satisfy the relationship of the reduction rate. V ′ / V = 0.5 to 2.5 (I) [wherein, V ′ represents the volume (cm ³ ) of the sheet after immersion in tetrahydrofuran at 25 ° C. for 24 hours, and V represents the volume of the sheet before immersion. (Cm ³ ). (W−W ′) / W × n _PS ≧ 0.7 (II) wherein W ′ represents the weight (g) of the sheet after immersion in tetrahydrofuran at 25 ° C. for 24 hours, and W represents the weight before immersion. The sheet weight (g) is shown, and n _PS is the styrene resin content ratio (% by weight) of the sheet before immersion. In the formula (I), V ′ / V is preferably 0.6 to 2.V.
0, particularly preferably 0.7 to 1.8. In the formula (II), (W−W ′) / W × n _PS is preferably from 0.75 to 1.0, particularly preferably from 0.8 to 1.
0.

The foamed thermoplastic resin sheet obtained by the production method of the present invention preferably has an expansion ratio of 1.05 to 3.0.
Times, particularly preferably 1.1 to 2.2 times, and the thickness is preferably 0.3 to 2.0 mm, particularly preferably 0.5 to 2.0 times.
1.0 mm.

The thermoplastic resin sheet and the thermoplastic resin foam sheet obtained by the production method of the present invention may be formed by laminating a resin non-foam sheet made of the same or different material on one or both surfaces to form a laminate of two or more layers. can do. The resin non-foamed sheet used in this case is used and properties to be imparted, for example, heat resistance, abrasion resistance, improvement of surface appearance,
It can be appropriately selected from desired materials according to printability and the like. Known methods such as a co-extrusion method and a dry lamination method can be applied as a method for manufacturing the laminate.

The thermoplastic resin sheet and the thermoplastic resin foam sheet obtained by the production method of the present invention can be coated with a conductivity-imparting agent, an antistatic agent, silicone and the like.

A container having a desired shape can be formed using the thermoplastic resin sheet and the thermoplastic resin foam sheet obtained by the production method of the present invention. The term “container” used herein includes a main body and a lid. For example, a container for a side dish includes a tray and a lid. This container
It is suitable as a food container, especially a food container with a high oil content, but of course is not limited to them, and various instant food containers of a type in which boiling water is poured, paper cups, containers heated with a microwave oven, etc. It can also be applied to containers that are heat-sterilized at the time of use and use, various non-heated containers, and the like.

[0031]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

The details of each component used below are as follows. (A) Component GPPS: Styrene resin ("Daicel Styrol 51" manufactured by Daicel Chemical Industries, Ltd.) HIPS: High impact polystyrene resin ("Daicel Styrol S85" manufactured by Daicel Chemical Industries, Ltd .; rubber content 8% by weight) SBS : Styrene-butadiene block copolymer ("Taphrene 126" rubber content 60% by weight, manufactured by Asahi Chemical Industry Co., Ltd.) (B) Component PP: Polypropylene (Sumitomo Chemical Industries, Ltd. "FS-
8611 ") PC: Polycarbonate (" Iupilon E-2000 "manufactured by Mitsubishi Gas Chemical Co., Ltd.) PET: Polyethylene terephthalate (" Dianight MA521H "manufactured by Mitsubishi Rayon Co., Ltd.) PA: Polyamide (nylon 6) (Ube Industries, Ltd.) ) "1030B") (Compatibilizer) Styrene-ethylene-propylene-styrene copolymer ("Septon 2104" manufactured by Kuraray Co., Ltd.).

Examples 1 to 8 and Comparative Examples 1 to 9 Compositions (A) and (B) shown in Table 1 are indicated by weight%.
The compatibilizer is expressed in parts by weight based on the components (A) and (B). ] Resin composition of twin screw extruder (Ikegai Co., Ltd .; PC
After melt-kneading according to M30), the extruded strand was cut to obtain resin pellets. The resin pellets were supplied to an extruder (PG-65-32 type extruder manufactured by Plagiken Co., Ltd.), melt-kneaded, and extruded from a T-die to obtain a thermoplastic resin sheet. Note that L / D
The ratio was adjusted by changing the adapter length.
Each evaluation test was performed on the obtained thermoplastic resin sheet by the following method. Table 1 shows the results. In Table 1, “continuous” indicates a bicontinuous phase structure, and “sea-island” indicates a sea-island structure.

(1) Judgment of Phase Structure of Sheet The thermoplastic resin sheet was cut with an ultramicrotome so that the surface became smooth. After that, the cutting surface is
O ₄ , OsO _{4 and} other heavy metal oxide vapors,
Only the styrene resin of the component (A) was selectively dyed.
Furthermore, after carbon was vapor-deposited on the stained surface, observation was performed with a scanning electron microscope, and it was determined from the distribution of reflected electron dose whether the structure had a bicontinuous phase structure or a sea-island structure.

(2) Container Formability A single-shot vacuum forming machine manufactured by Asano Laboratories was used.
m, forming a cup container with a bottom diameter of 80 mm and a height of 50 mm,
The container was inspected visually for corners (the portion where the bottom surface and the side surface are in contact) and side surfaces, and the surface condition (appearance and gloss), and evaluated according to the following criteria. ：: No breakage and good surface condition were obtained. Δ: No tear, but uneven unevenness on the surface. X: There was a break.

(3) Appearance of Container The appearance of the cup container obtained in the container moldability test was visually observed and evaluated according to the following criteria. ：: The surface is smooth and glossy. Δ: The surface is rough and there is no gloss. X: The surface roughness is severe and the feel is rough.

(4) Strength of container waist Using a tensile tester (R-500) manufactured by Shimadzu Corporation, the cup container obtained in the container moldability test was compressed at a crosshead speed of 10 mm / min. The maximum load at which the container buckled was determined, and the strength of the waist was evaluated according to the following criteria. ：: 20 kgf or more. Δ: 15 kgf or more and less than 20 kgf. X: Less than 15 kgf.

(5) Impact resistance of container 200 g of water was placed in the cup container obtained in the container moldability test.
Drop on a concrete surface from a predetermined height
%, And the impact resistance was evaluated according to the following criteria. ：: 50 cm or more. Δ: 10 cm or more and less than 50 cm. ×: less than 10 cm.

(6) Heat Resistance 100 g of food-grade salad oil (manufactured by Nisshin Oil Co., Ltd.) was placed in the cup container obtained in the container moldability test, and heated in a 500 W microwave oven for 3 minutes. The degree of deformation of the container after heating was visually observed and evaluated according to the following criteria. ：: No deformation. Δ: There is some deformation. ×: Deformation is severe.

(7) Oil Resistance A 10 cm square sheet was immersed in a salad oil for food (manufactured by Nisshin Oil Co., Ltd.), and allowed to stand at 20 ° C. for 3 days. Thereafter, the sheet was taken out and visually observed, and the presence or absence of cracks and the degree of swelling were evaluated according to the following criteria. ：: No crack was generated and no swelling was observed, and no change was observed. Δ: Both crack generation and swelling are slightly observed. X: Crack generation and swelling were both remarkable.

[0041]

[Table 1]

As is clear from Examples 1 to 8, by adjusting the L / D ratio of the pipe and the flow rate of the resin composition in the pipe, the phase structure of the sheet can be changed to a bicontinuous phase structure. As a result, a sheet and a container having well-balanced properties were obtained.

Examples 9 to 16 and Comparative Examples 10 to 18 Resin pellets were produced in the same manner as in Examples 1 to 8, using the resin compositions having the compositions shown in Table 2 (the same display criteria as in Table 1). One part by weight of mineral oil was spread on the resin pellets, and a mixture of sodium bicarbonate and sodium citrate (manufactured by Sankyo Chemical Co., Ltd .; CellMike 623) as a foaming agent was added in an amount (weight) shown in Table 2. (Part indication) A mixed resin composition for a resin foam sheet was obtained. This resin composition was fed to the same extruder as in Examples 1 to 8, melted and kneaded.
Foaming was performed while extruding from a die to obtain a thermoplastic resin foam sheet. The L / D ratio was adjusted in the same manner as in Examples 1 to 8. The same evaluation tests as in Examples 1 to 8 were performed on the obtained thermoplastic resin foam sheet. Table 2 shows the results. In Table 2, “continuous” indicates a bicontinuous phase structure, and “sea island” indicates a sea island structure.

[0044]

[Table 2]

As is apparent from Examples 9 to 16, by adjusting the L / D ratio of the pipe and the flow rate of the resin composition in the pipe, the phase structure of the sheet can be made a bicontinuous phase structure. As a result, a sheet and a container having well-balanced properties were obtained.

[0046]

According to the production method of the present invention, the thermoplastic resin sheet and the thermoplastic resin foam sheet can have a bicontinuous phase structure. For this reason, since the property which the component (A) and the component (B) originally have can be sufficiently exhibited, the appearance such as moldability, surface gloss and smoothness can be improved.
A sheet having excellent rigidity (strength), impact resistance, heat resistance, oil resistance and the like can be obtained.

Continued on the front page F term (reference) 4F207 AA13 AB09 AB11 AB12 AB13 AG01 AG20 AH58 AM32 AR12 AR14 AR15 KA01 KA11 KA17 KB22 KL55 KL84 KM02 KM15 4J002 BB12X BB15X BB17X BC03W BC03X BC04W BC06W BC07W BC08W BC07W BC08W BC07W BC08X CF08X CG01X CH07X CH09X CK02X CL01X CL03X CL05X CL06X CN01X CN03X DE226 EA016 EQ036 ET006 FD010 FD326 GG01

Claims (3)

[Claims] (A) 40 to 98% by weight of a styrene resin
And (B) the melting temperature specified by JIS K7121 is 1
Crystalline thermoplastic resin 60 to 300 ° C.
When a resin composition containing 2% by weight is melt-kneaded by an extruder and extruded, the L / D ratio of a pipe connecting an extruder outlet and a molding die is set to 25 or more, and the resin in the pipe is set. A method for producing a thermoplastic resin sheet, wherein the flow rate of the composition is adjusted to 100 to 50,000 g / min. 2. (A) 40 to 98% by weight of a styrene resin
And (B) the melting temperature specified by JIS K7121 is 1
Crystalline thermoplastic resin 60 to 300 ° C.
When the resin composition containing 2% by weight is melt-kneaded by an extruder and subjected to extrusion foam molding, the L / D ratio of a pipe connecting an extruder outlet and a molding die is set to 25 or more, and A method for producing a thermoplastic resin foam sheet, wherein the flow rate of the resin composition is adjusted to 100 to 50,000 g / min. 3. The method for producing a thermoplastic resin foam sheet according to claim 2, wherein the expansion ratio of the thermoplastic resin foam sheet is 1.05 to 3.0 times and the thickness is 0.3 to 2.0 mm.