JP3000471B2 - Low temperature high formability stretched sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to styrene, which is mainly subjected to secondary molding by means such as vacuum molding and air pressure molding, and which is suitably used for packaging lightweight food packaging containers and other articles. Stretched sheet made of resin-based resin composition, more specifically, excellent in rigidity (elastic modulus), optical properties, toughness, etc., moldability in secondary molded articles by vacuum molding, pressure molding, etc., deep drawability The present invention relates to a stretched sheet of a styrene-based resin composition having improved high-speed moldability, low-temperature moldability, etc., and giving a secondary molded product with less uneven thickness.

[Prior art] Conventionally, rigid vinyl chloride (PVC) sheets and stretched styrene-based polymer sheets are generally known as general packaging sheets in the field of rigid plastic sheets. It is secondarily formed by a method such as a method, and is used in many packaging containers for foods and the like.
Of these, for secondary molded products with a drawing ratio of 0.5 or more,
In the case of a styrene-based polymer stretched sheet, it is difficult to faithfully reproduce the shape of the mold due to the stretch orientation of the sheet at the normal secondary molding temperature. There is a disadvantage that the thickness becomes extremely thin, and further, whitening, tearing, and the like are easily caused. In order to solve these problems, when the molding is performed at a relatively high temperature, the orientation of the sheet is relaxed, the molded product becomes brittle at a portion where the drawing ratio is small, and the molded product is easily broken. When a sheet is heated and formed by the method, unevenness of a flat part of a formed product caused by contact unevenness between a sheet and a hot plate, which is referred to as raindrop, is generated, and the commercial value is lost. For this reason, at present, hard PVC sheets (containing about 10 to 30% by weight of a plasticizer) are used for deep drawing. However, a rigid PVC sheet has a problem of pollution due to chlorine-based gas generated at the time of combustion, in addition to a problem of hygiene and quality of a plasticizer, and a sheet replacing the PVC sheet is required.

In order to solve the above problems, there has been proposed a method of laminating a polyolefin-based resin on a stretched styrene-based polymer sheet to improve deep drawability and mold reproducibility. For example, JP-A-49-18976 discloses general-purpose polystyrene (G
PPS) A composite sheet obtained by dry laminating an unstretched polypropylene sheet on a stretched sheet via an adhesive,
JP-A-55-114458 discloses a composite stretched sheet obtained by laminating a polyolefin layer such as low-density polyethylene or polypropylene on a GPPS layer via an adhesive layer by a coextrusion method, a dry lamination method, or the like, and then stretching. ing. However, in these methods, since the olefin resin is disposed on the surface layer, transparency and rigidity are poor. Furthermore, since different kinds of resins are laminated, for example, sheet scraps after punching of a secondary molded product, gripping margins during sheet formation, and the like cannot be effectively collected, which is economically disadvantageous.

Japanese Patent Publication No. 51-5682 discloses a molding comprising a composition comprising a styrene-butadiene block copolymer (SBBC) containing 60 to 90% by weight of a styrene-based hydrocarbon and a small amount of a hardened oil of animal or vegetable oil. There is a description of a non-stretched sheet for use. Although it can be formed by deep drawing, it is inferior in rigidity especially in a secondary molded product because it is a single SBBC and a non-stretched sheet, and is liable to be clouded and has insufficient transparency.

Further, a method of blending SBBC with a styrenic polymer is disclosed in, for example, JP-A-49-98857.
A method of blending with a mixture of S and high impact polystyrene (HIPS) is disclosed in JP-A-58-129038 and JP-A-59-4993.
No. 8 and JP-B-62-31017. These are intended to improve the impact resistance and toughness of the styrene polymer sheet / film by SBBC, and a stretched sheet composed of these compositions has little effect of improving the secondary formability. Furthermore, these methods deteriorate the transparency and rigidity of the resin. In particular, when a resin is stretched after melt extrusion to form a sheet, the micro flow difference between GPPS and SBBC blend particles and the anisotropy during stretch orientation depend on the temperature conditions during extrusion and stretching. However, there is a problem that the transparency is further deteriorated because these have different temperature dependences. For this reason, the temperature conditions during extrusion and stretching are narrowed,
The performance of the resulting sheets also tends to be limited.

JP-A-61-25819 discloses a low-temperature shrinkable film comprising a styrene-butyl acrylate copolymer. This method provides a styrene-based polymer low-temperature shrinkable film having improved low-temperature shrinkage, elastic modulus, crack resistance, and optical properties by imparting low-temperature stretchability. For this reason, it is different from the stretched sheet excellent in the secondary formability intended in the present invention. Further, since this film is stretched at a low temperature, the heat shrinkage stress becomes high. For this reason, when the secondary molding is performed, the effect of improving the moldability such as the deep drawability is not exhibited as compared with the stretched styrene polymer sheet.

As described above, in any of the methods, in the stretched styrene-based resin sheet, the secondary moldability, particularly the deep drawability and the mold reproducibility are improved without impairing the transparency and rigidity, which are the characteristics of the styrene-based resin. It is difficult at present.

[Problem to be Solved by the Invention] Further, since the unit price of the secondary molded article of the stretched styrene polymer sheet is very low, increasing the molding speed greatly contributes to the improvement of profit. For this reason, secondary molding manufacturers control the molding cycle in units of 0.5 seconds or less, and the development of stretched styrene polymer sheets that can shorten the molding cycle is awaited. Also, at the start of operation or at the start-up after changing the mold of the molding machine, the stretched styrene polymer sheet needs to be molded at a higher temperature than the PVC sheet, so it takes a relatively long time until it can be molded stably. During this time, there is a disadvantage that defective products are easily generated. For this reason, a sheet that can be secondarily formed at a low temperature is also useful for a molding manufacturer to improve profitability.

The present invention is a styrenic resin composition having improved impact resistance, high-speed moldability, and low-temperature moldability while maintaining transparency and rigidity, which are features of the styrene-based resin sheet in the above situation. To provide a stretched sheet,
It is an object of the present invention to provide a highly formable stretched sheet having improved mold reproducibility, deep drawability, and uneven thickness in a secondary molded product by pressure forming, vacuum forming, or the like.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, at least one kind of monomer selected from styrene or a styrene-based derivative: 97 to 20% by weight; At least one copolymer (A) having a Vicat softening point of less than 90 ° C. and a monomer comprising the carboxylic acid or a derivative thereof: 3 to 80% by weight; 20% by weight and at least one kind of conjugated diene monomer: 5 to 80% by weight. ASTM D-1504 comprising a resin composition mainly composed of a mixture of the copolymer (B) and a copolymer having a weight mixing ratio of the copolymers (A) and (B) of 0.05 ≦ A / (A + B) ≦ 0.99. Heat shrinkage stress (ORS) measured according to 2.0 to 15 kg / cm ² And is calculated from the following equation
A sheet for secondary molding stretched and oriented in a biaxial direction having an ORS relaxation rate of 0.70 to 0.3 or the resin composition: 95 to 5% by weight, and at least one monomer selected from styrene or a styrene-based derivative (A) Excluding the resin contained in the copolymer (A) (C): 5 to 95% by weight, as measured according to ASTM D-1504. Heat shrinkage stress (ORS) 2.0 ~ 15kg / cm ² ,
And the ORS relaxation rate obtained from the following equation is 0.70 to 0.32
A sheet for secondary molding stretched and oriented in the axial direction was employed.

ORS relaxation rate = (ORS-2 / ORS-1) ORS-2: The sheet was immersed for 3 seconds under tension in silicon oil at 40 ° C. higher than the Vicat softening point of the resin composition constituting the sheet. Later ORS Hereinafter, the present invention will be described in detail.

Copolymer (A) In the present invention, styrene or a styrene-based derivative (hereinafter, referred to as a styrene-based component), which is one of the components constituting the copolymer (A), includes, for example, styrene, α-alkyl-substituted styrene, and the like. And at least one selected from alkyl-substituted styrenes, halogen-substituted styrenes, etc., depending on the purpose. The content of the styrene component in the copolymer (A) is 97 to 20% by weight.
Need to be If the styrene component is less than 20% by weight, the rigidity, which is a characteristic of the styrene component, is undesirably weak. Further, from the viewpoint of increasing the fluidity of the resin, improving the moldability during melt extrusion, and increasing the compatibility with the block copolymer (B), the styrene component is used in an amount of 97 to 100%.
Preferably it is 40% by weight, more preferably 95 to
It is 50% by weight, more preferably 95-60% by weight. When the styrene component exceeds this upper limit, the effect as the aliphatic unsaturated carboxylic acid or a derivative thereof (hereinafter, referred to as a carboxylic acid component) (for example,
Solvent resistance, weather resistance, and the like, when the third component is added, and the like, such as improvement in the mixing property and reactivity with the third component), and the like.
Not preferred.

The carboxylic acid component as the other component of the copolymer (A) includes acrylic acid or its esters, methacrylic acid or its esters, α, β such as fumaric acid, maleic acid, and itaconic acid. -At least one may be selected from unsaturated dicarboxylic acids and the like or mono- or diesters thereof according to the purpose. Among these, preferred are those based on the above esters, and these alcohol components are ethyl, propyl, butyl,
Pentyl, hexyl, carbon atoms octyl ... etc. C ₂ -C ₁₂
Is an ester comprising an alcohol having a linear or side chain, preferably an alcohol having the same C _{2 to} C ₈ . The acid component of the ester is preferably an acrylic acid or methacrylic acid type, and more preferably the former.

The copolymer (A) is a copolymer of these styrene-based components and carboxylic acid-based components. These are copolymers composed of at least one type of monomer, and if necessary, may be a copolymer of at least two types of styrene-based components and carboxylic acid-based components. Further, a mixed polymer composition containing at least one of these copolymers may be used.

Further, the solvent resistance of the low-temperature high-formability stretched sheet of the present invention,
From the viewpoint of improving stress crack resistance, the carboxylic acid component in the copolymer (A) may be a mixture of two kinds of a carboxylic acid ester and a carboxylic acid. Part is metal ion (Na ⁺ , Li ⁺ ,
K ⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Mg ²⁺ , Zn ²⁺ , Fe ²⁺ , Fe ³⁺ , etc.). In that case, the ratio of the monomer equivalent unit having an ionic bond is 10 to 0.0005 mol%, preferably 5 to 0.001 mol%, more preferably 3 to 0.05 mol% in the copolymer. The method of introducing the ionic bond may be carried out by a known method, for example, in the form of a salt before the polymerization, in the form of a neutralization after the polymerization, or after introducing the saponified carboxylic acid ester after the polymerization, It is not limited to these. Further, in this case, if the ratio of the monomer equivalent unit having an ionic bond exceeds 10 mol%, the flow during melt extrusion, particularly the processability and the mixing property, are not preferable.

As the copolymer (A) composed of the above monomers, one kind may be used, or two or more kinds may be mixed.
ASTM D
Vicat softening point (hereinafter abbreviated as VSP: weight 1 kg, heating rate 2 ° C / min) measured according to -1525 is less than 90 ° C, preferably 85 ° C or less, more preferably 80 ° C or less. Is preferred. Although the lower limit is not specified,
In general, a temperature of about 25 ° C. or more, preferably about 30 ° C. or more, and more preferably about 40 ° C. or more is good. The upper limit of VSP is one of the effects of the present invention, which is one of the effects of the present invention. The secondary formability of the stretched sheet (the forming temperature range when the stretched styrene polymer sheet is formed into a container by a pressure forming method, a vacuum forming method, etc., (Shows uneven thickness, low-temperature moldability, high-speed moldability, deep drawability, etc.). In addition, the preferable lower limit is generally a point that hinders the handling of the copolymer, particularly a region where stickiness occurs when used in a large amount, and this is not limited when these measures are taken.

The copolymer constituting the component (A) has a solution viscosity at 25 ° C. of a toluene solution having a concentration of 10% by weight of the copolymer (A) (Canon-Fence viscosity tube No. 200) as a measure of the molecular weight. ), Preferably 5 to 100 cps, more preferably 10 to 80 cps, and still more preferably 15 to 60 cps (5, 10, 50, and 100 cps each have a weight average molecular weight of about 7.
60,000, 150,000, 410,000 and 560,000). These upper limits are limited by the processability and mixing properties of the resin. The lower limit is limited by the strength, processability, dispersibility, etc. of the copolymer itself.

The method for producing the copolymer (A) is generally random polymerization by radical thermal polymerization and mass polymerization using a part of a solvent, but is not limited thereto. In addition, it is sometimes more preferable to add a high-impact formulation by incorporating known rubbers as a third component before or after polymerization to incorporate a formulation such as grafting or homogenization and matrix incorporation. (A) is a copolymer including these materials.

Block copolymer (B) The block copolymer (B) used in the stretched sheet at low temperature and high moldability according to the present invention includes at least one block containing a styrene component as a main component and a conjugated diene as a main component. Means that at least one block is linearly or non-linearly (branched). The styrenic component constituting the block copolymer (B) may be, for example, styrene, α-
Alkyl-substituted styrenes, such as α-methylstyrene,
At least one kind may be selected from alkyl-substituted styrene, halogen-substituted styrene, and the like according to the purpose.

Further, the monomer comprising a conjugated diene is an olefin having a conjugated double bond, for example, 1,3-butadiene,
2-methyl-1,3-butadiene, 1,3-pentadiene, 1,
3-hexadiene or the like;
You can choose the species. Of these, preferred are 1,3-butadiene and 2-methyl-1,3-butadiene.

Further, a block obtained by hydrogenating a part or all of the double bond of the conjugated diene in the block copolymer (B) or a block obtained by modifying a part of the double bond with an unsaturated carboxylic acid such as acrylic acid or maleic anhydride. Copolymers may be used alone or as a mixture. Further, at least one part of the molecular structure of each of the above groups may include a part having a random structure, or may include another copolymerizable monomer.

The ratio of the styrene component constituting the block copolymer (B) to the monomer comprising a conjugated diene is 95 to 20% by weight of the former resin, preferably 90 to 30% by weight, and more preferably. Is from 85 to 50% by weight. The upper limit is a region where the effect of reinforcing the rubber component, for example, the effect of improving impact resistance is difficult to be exhibited. Further, the lower limit is a region where the rigidity and heat resistance of the obtained sheet are reduced, and the thermal stability of the resin is also deteriorated, so that gel is easily generated at the time of melting.

The polymer block mainly composed of a styrene component is preferably a number average molecular weight of 0.5 × 10 ⁴ or more, more preferably 0.7 × 10 ⁴ to 10 × 10 ⁴ , and still more preferably 1.0 × 10 ⁴ to 8.
About × 10 ⁴ .

The lower limit is not preferable because the hardness and strength of the block copolymer (B) are reduced or the properties as the block copolymer (B) are impaired, and the upper limit is because the effect of the rubber component is exhibited. Or it is a level in terms of workability. The molecular weight (in terms of butadiene) of the polymer block mainly composed of a conjugated diene is preferably 1,000 to 20 × 10 ⁴ ,
More preferably 5,000 to 10 × 10 ⁴ , even more preferably 1 × 10 4
⁴ to 10 × 10 ⁴ , and 2 × 10 ⁴
It is about 100 × 10 ⁴ , preferably about 2 × 10 ⁴ to 50 × 10 ⁴ , and more preferably about 3 × 10 ⁴ to 40 × 10 ⁴ (each of which is represented by a number average molecular weight).

The method of measuring the molecular weight is determined by the charge ratio and the amount of the catalyst, which is a feature of the ionic polymerization method, and can be easily determined.

Next, the way of bonding each block is related to the manufacturing method.Basically, if a block segment mainly composed of a styrene component is: S, and a block segment mainly composed of a conjugated diene is: D, One group includes linear blocks having a basic structure represented by (DS) _{n + 1} , (DS) _n -D, S- (DS) _n (where n = 1 to 10). It is a polymer, and its production method is based on a means of performing block copolymerization using a polymerization initiator such as an organic lithium-based compound in a hydrocarbon-based solvent.

The next group is [(DS) _n ] _{m + 2} X, [(S−
D) _n ] _{m + 2} X, [(S−D) _n −S] _{m + 2} X, [(DS)
_n- D] _{m + 2} X is a non-linear block copolymer having a branched basic structure such as (where n = 1 to 10, m = 1
To 10), (X represents the residue of a polyfunctional initiator, e.g., initiator SiCl _4, SnCl ₄ polyfunctional organolithium compounds, polyepoxides, polyisocyanates, polyaldehydes, polyketones, tetraallyl Sn, etc.).

Among the above preferred embodiments, the linear block copolymer has n = 1 to 5, preferably n = 1 to 3, more preferably n
= 1-2.

In the case of a non-linear block copolymer, m = 1 to 5 and n =
1 to 5, preferably m = 1 to 3 and n = 1 to 3, more preferably m = 1 to 2, and n = 1 to 2.

These production methods are described, for example, in JP-B-36-19086,
-14979, 48-2423, 48-4106, 49-36957, 51-27701, etc., but in the present application, those in the specific range described above are used. And

In the stretched sheet at low temperature and high moldability according to the present invention, the VSP of the resin composition of the copolymer (A) and the block copolymer (B) is 55 ° C. or higher, preferably 60 ° C. or higher, more preferably 70 ° C. It is better to do above. A temperature lower than this temperature is a region where the heat resistance of the sheet and the secondary molded product in practical use is insufficient, and the rigidity tends to decrease.

In the stretched sheet at low temperature and high moldability according to the present invention, the mixing composition ratio of the main copolymer (A) and the block copolymer (B) is 0.05 ≦ A / (A + B) ≦ 0.99 by weight.
And preferably 0.25 ≦ A / (A + B) ≦ 0.97,
More preferably, 0.40 ≦ A / (A + B) ≦ 0.95, and even more preferably 0.60 ≦ A / (A + B) ≦ 0.90.

Below these lower limits, the secondary formability, rigidity,
This is a region where the thermal stability when extruding the resin is insufficient, which is not preferable. The upper limit is a region where the toughness of the sheet or the secondary molded product is reduced. Even if the toughness of the sheet is at a level that can withstand practical use, the secondary molded product is at a level where the orientation of the sheet is relaxed and the portion where the drawing ratio is shallow is brittle.

In order to obtain a low-temperature high-formability stretched sheet of the present invention, a non-stretched sheet may be formed from these resin compositions (A) + (B) by a known method and biaxially stretched (an example will be described later). ).

Further, in the low-temperature high formability sheet of the present invention, if necessary, 95 to 5% by weight of the resin composition (A) + (B) may contain at least one monomer selected from styrene or a styrene-based derivative. Styrene-based polymer whose main component is (excluding the resin contained in the copolymer (A)) (C): 5
The secondary moldability can also be improved when a stretched sheet is formed by a known method using a mixed resin composition of about 95% by weight.

Styrene-based polymer (C) In the stretched sheet at low temperature and high moldability of the present invention, the styrene-based polymer (C) refers to, for example, styrene, α-alkyl-substituted styrene such as α-methylstyrene, nucleated alkyl-substituted styrene, nucleus 50% by weight of a polymer comprising at least one styrene monomer selected from halogen-substituted styrene, or at least one of the styrene monomers
As described above, a copolymer of a styrene-based monomer and a copolymerizable monomer, preferably 70% by weight or more, and an impact-resistant polystyrene containing a small amount of a rubber component. These polymers may be used alone or in combination of two or more.

Examples of monomers copolymerizable with the monomer forming the styrene-based polymer include acrylic acid or an ester thereof, methacrylic acid or an ester thereof, maleic acid, fumaric acid, and α-β-acids such as itaconic acid. Examples include unsaturated dicarboxylic acids or their monoesters, diesters, acrylonitrile, maleic anhydride, and maleimide. These monomers may be used alone or in combination of two or more, but exclude the resin contained in the above-mentioned copolymer (A).

Among these styrenic copolymers (C), preferred are general-purpose polystyrene or esters of C _{1 to} C ₁₂ alcohols with acrylic acid, methacrylic acid, etc .: 5 to 50% by weight.
And styrene: 95 to 50% by weight, and is a resin not included in the above-mentioned copolymer (A) having a Vicat softening point higher than 90 ° C. In order to improve oil resistance, weather resistance, and the like, a copolymer of acrylonitrile, methyl methacrylate, methacrylic acid, maleic anhydride, or the like with the styrene monomer may be preferable.

When a general-purpose polystyrene is used as the styrene-based polymer (C), its weight average molecular weight (measured by a GPC measurement method) is 100,000 to 600,000, preferably 150,000 to 500,000, more preferably 20 to 40,000. It is a million. The upper limit of the weight average molecular weight is a region where the deterioration of the secondary moldability and the mixing property with the copolymer (A) and the block copolymer (B) are deteriorated. The lower limit is that the strength of the sheet is reduced, and when the secondary forming is performed by the pressure forming method, the unevenness of the contact between the sheet and the hot plate of the forming machine causes irregularities in the flat part of the molded product, so-called raindrop, which is a defect. This is an area in which is likely to occur.

When using a copolymer of the ester and styrene as the styrene polymer (C), eg, C ₁ methyl, ethyl, propyl, butyl, hexyl, ... etc.
Alcohol and acrylic acid -C _12, Vicat softening point not contained in the copolymer (A) of the present invention with copolymers of esters of styrene and methacrylic acid preferably has a high temperature from 90 ° C..

These styrene-based polymers (C) are preferably mixed in an amount of 5 to 95% by weight based on the whole resin composition constituting the sheet. Among them, a resin composition composed mainly of the above-mentioned copolymer (A) and block copolymer (B): a composition in which 95 to 50% by weight and a styrene-based polymer (C): 5 to 50% by weight are arranged. The sheet made of the product can further improve rigidity and heat resistance while maintaining good secondary moldability of the resin composition (A) + (B) sheet. The styrene polymer (C): 50 to 95% by weight of the resin composition (A) + (B): 50 to 95% by weight.
The sheet made of the composition in which 5% by weight is provided has a feature of further improving the toughness and secondary moldability of the styrene-based polymer (C) sheet.

As described above, the above mixing range is an amount necessary to exhibit the characteristics of both resins to be mixed. That is, when the styrene-based polymer (C) is less than 5% by weight, the resin composition (A)
+ (B) It is not sufficient to further improve the heat resistance and rigidity of the sheet. Conversely, if it is more than 95% by weight, the toughness of the styrene polymer (C) sheet should be improved. It is difficult.

In order to further balance the secondary formability of the sheet, the heat resistance of the sheet and its molded product, and the toughness, the mixing amount of the styrene polymer (C) is preferably from 10 to 90.
%, More preferably 20-80% by weight.

In this case, a preferable condition for exhibiting the effect of the present invention described above is to set the Vicat softening point of the entire mixed resin composition.
It is desirable to select the styrenic polymer (C) at a temperature of 55 ° C. or more and 105 ° C. or less. In particular, when a high degree of low-temperature moldability is exhibited, the Vicat softening point of the entire polymer mixture composition is preferably 95 ° C or less, more preferably 90 ° C or less.
It is more desirable to select the styrenic polymer (C) at a temperature of not more than ° C.

The stretched sheet at low temperature and high moldability of the present invention is formed into a film by a known method and stretched from the mixed resin composition obtained by further adding the styrene polymer (C) to the resin composition (A) + (B). It can also be obtained by:

The low-temperature, high-formability stretched sheet The method of mixing the resin used in the low-temperature, high-formability stretched sheet of the present invention is a method by dry blending, a method of sufficiently kneading with a mixer having a high kneading capacity, and a method of pelletizing, and a common goodness of each main component resin. A method of pelletizing after melting with a solvent,
A known method may be used as appropriate, such as a method using a good solvent and a poor solvent, and the method is not limited thereto.

The method for producing the sheet of the present invention is not particularly limited, and may be performed by a method commonly used in the production of a conventional stretched sheet. One example is a mixture obtained by mixing the above-mentioned copolymer (A), the block copolymer (B), and, if necessary, other admixtures and general plasticizers, followed by dry blending or premixing. Is continuously extruded with a T-die or a circular die, and the raw material is biaxially stretched successively or simultaneously by a tenter method or a bubble method. Alternatively, a compression sheet may be prepared and stretched by a batch method.

These stretching ratios are 1.5 to 8 times, preferably 2 to 6 times in one direction. The stretching temperature is 10 to 50 ° C. higher than the VSP of the resin composition forming the sheet, preferably 15 to 45 ° C.
℃ high temperature, more preferably 15 to 40 ℃ high temperature. In addition, in particular, in the second-stage stretching in the sequential biaxial stretching or simultaneous biaxial stretching, the stretching temperature is higher than the VSP of the resin composition forming the sheet by 15 to 50 ° C., preferably 20 to 40 ° C. High temperature is good.

The thickness of the low-temperature high-formability stretched sheet of the present invention is 0.05 to 1.
0 mm, preferably 0.08 to 0.8 mm, more preferably 0.1 to 0.8
mm, more preferably in the range of 0.12 to 0.6 mm.

Further, the stretched sheet at low temperature and high formability of the present invention may be used as a new next component in addition to the copolymer (A), the block copolymer (B), and the styrene-based polymer (C) which are resins usable therein. For example, release agents, heat stabilizers, slip agents, antistatic agents, ultraviolet absorbers, antifogging agents, antioxidants, coloring agents, plasticizers, oligomers, other conventional additives, petroleum resins, and other polar groups A homopolymer or a copolymer having the same may be mixed as long as the characteristics of the present invention are not impaired.

Further, since the polymers constituting the low-temperature high-formability stretched sheet of the present invention have good compatibility with each other, it is possible to effectively collect a gripping margin at the time of film formation, an extruded waste, a waste at the time of secondary molding, and the like, and are economical. It is also possible to use these recovered polymers as a part of the resin of the present invention as long as the transparency is not deteriorated.

The orientation level of the stretched sheet at low temperature and high formability of the present invention is determined by the heat shrinkage stress (OR) measured according to ASTM D-1504.
S: Vicat softening point of resin composition forming sheet + 30 ° C
The peak stress value in silicone oil at a temperature of 2.0 to 15 kg /
Suitably, it is in the range of cm ² , preferably in the range of 2.5 to 12 kg / cm ² , more preferably in the range of 3.0 to 10 kg / cm ² . Above this upper limit, it is an area where mold reproducibility of the molded article is deteriorated when the secondary molding is performed by a usual molding machine, and furthermore, the product is cracked and whitened by the influence of excessive orientation, which is not preferable. Below the lower limit, the orientation level is low, so that the toughness decreases.Also, even if the sheet has toughness that can withstand practical use, deorientation occurs at the stage of secondary molding, and when punching out a molded product, This is an area where cracks may occur.
In addition, it is a region where it is difficult to improve rigidity due to the stretching effect.

In the low-temperature high-formability stretched sheet of the present invention, in order to impart deep drawability and high-speed moldability and obtain a molded product with less uneven thickness, the orientation relaxation rate after heat-treating the sheet under tension is important. . In the present invention, the resin composition constituting the sheet
ORS measured by the above method after immersing the sheet under tension in silicone oil at 40 ° C higher than VSP for 3 seconds
The ORS relaxation rate obtained from the ratio of (ORS-2) to the ORS (ORS-1) of the sheet before treatment = (ORS−2 / ORS−1) was used as the scale.

In the present invention, the ORS relaxation rate is 0.70 or less, preferably 0.65 or less, more preferably 0.60 or less. Also,
The lower limit is 0.30 or more. The upper limit of the ORS mitigation rate is 2 for the sheet
This is a level at which it is difficult to improve the secondary formability, particularly the deep drawability and high-speed formability. Further, a preferred lower limit is
This is a level at which the toughness of the sheet is reduced due to relaxation of the stretching orientation of the general sheet, and the sheet is brittle at a portion having a small drawing ratio such as a flange portion of the secondary molded product, and the secondary molded product is easily broken.

The major feature of the low-temperature high-formability stretched sheet of the present invention is that
This is an improvement in toughness and an improvement in toughness, particularly in the point that deep drawing can be performed.

In general, it is difficult to form a drawn sheet of a styrene-based polymer by deep drawing (the usual drawing method has a limit of about 0.5 in drawing ratio). It is believed that the reason for this is that due to the stretch orientation of the stretched styrene polymer sheet, resistance is exerted when the sheet is subjected to secondary molding. However, in the low-temperature high-formability stretched sheet of the present invention, regardless of the stretch-oriented sheet,
Deep drawing is possible. This is due to a synergistic effect of the copolymer (A) and the block copolymer (B). That is, by mixing the copolymer (A) and the block copolymer (B), the sheet is formed at a normal secondary molding temperature (for example,
The orientation relaxation (expressed by the relaxation of ORS) of the styrene-based polymer sheet or the copolymer (A) when subjected to tension heat treatment at a temperature at which molding can be performed without the occurrence of defects such as raindrops by the contact heating type pressure forming method. 2) Because it is larger than a single sheet,
When the sheet is stretched during the next molding, the resistance due to the orientation is reduced. For this reason, it is easy to mold, and the deep drawability is also improved. Further, for this reason, low-temperature moldability and high-speed moldability are also provided.

For example, a block copolymer (B) having a comparative ratio of -5 was added to 10
Weight percent of a general-purpose polystyrene sheet containing 140% by weight in silicone oil at 140 ° C for 3 seconds.
ORS is 83% before processing. Further, the ORS of the copolymer (A) alone sheet having a ratio of −4 was obtained by the same treatment at 120 ° C.
67%. On the other hand, for example, the sheet of Experiment No. 1 of Example 1 of the present invention has an ORS of about 51% by the treatment at 121 ° C. This orientation relaxation corresponds to forming a stretched styrene polymer sheet at about 20 ° C. higher than a normal secondary forming temperature. In this case, the stretched styrene-based polymer sheet can be obtained only in a portion where the draw ratio of the formed product is shallow, due to the influence of deorientation, and the product is brittle and easily cracked. However, in the stretched sheet at low temperature and high formability of the present invention, the copolymer (A)
The effect of improving the brittleness in low orientation by the synergistic effect of the polymer and the block copolymer (B) works, and a secondary molded product that can withstand practical use can be supplied. For example, the ORS level at which the bending strength, which is a substitute property of brittleness (toughness), becomes 15 or more times with a 250 μm sheet is a general-purpose polystyrene sheet containing 10% by weight of the block copolymer (B) (comparative example -5). ) Is about 4 kg / cm ² , for example, is about 2 kg / cm ^{2 in} the sheet of Experiment No. 1 in Example 1, and a large toughness improvement effect can be obtained even with low orientation.

Furthermore, the orientation of the sheet itself can be lowered due to the large toughness improving effect at the low orientation.
This is more preferable for the secondary formability. This effect is the same when the styrene-based polymer (C) is added to the resin composition (A) + (B) within the above-mentioned range, and the secondary moldability is improved as shown in Example 2. Is done.

Therefore, in the stretched sheet at low temperature and high moldability according to the present invention, a deep drawn product which cannot be imagined from a general styrene polymer stretched sheet can be obtained without lowering its practical strength.

The low-temperature, high-formability stretched sheet of the present invention is suitably used for a lightweight container for packaging, such as for food packaging, by a generally known method such as, for example, pressure forming, vacuum forming,
The use is not limited to these.

Further, the stretched sheet at low temperature and high formability of the present invention includes a container obtained by secondary forming the sheet of the present invention by a known method, and a sheet formed of another material (for example, a low-expansion polystyrene sheet, an impact-resistant polystyrene sheet, etc.). )), A sheet laminated by a known method, and a molded container thereof.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

 The evaluation method is as follows.

1) Tensile strength at break and elastic modulus were measured according to ASTM D-882. (Measured at 23 ° C and 60% relative humidity) Average value of warp and weft 2) Folding strength is ASTM D-
It was measured according to 2176. (Bend angle: 135 ゜ ± 2 on both sides
゜, tension load: measured at 1kg, 23 ℃, relative humidity 60%)
3) Haze was measured according to ASTM D-1003.

4) ORS is measured according to ASTM D-1504. (Peak stress value in silicone oil at the temperature of Vicat softening point of resin composition + 30 ° C) 5) The ORS relaxation rate is set so that the sheet is 150 x 150 mm and the width of the aluminum frame is 15 mm, so that there is no slack. The ORS (ORS-2: the average of the vertical and horizontal lengths) of the sheet that has been pasted, immersed in silicone oil adjusted to VSP + 40 ° C for each sheet composition for 3 seconds, and quenched before processing in the same direction as the ORS (ORS- 1: average of vertical and horizontal) (ORS-2 / ORS-1). ORS was measured in the same manner as in 4) above.

6) The low-temperature moldability, molding temperature range, and uneven thickness were evaluated by the following methods.

The test sheet is heated on a hot plate using a contact heating type air pressure molding machine.
Under the conditions of 70 to 170 ° C., a heating time of 2.5 seconds, a molding time of 2.0 seconds, and a molding pressure of 2.0 kg / cm ² , a transparent cylindrical container having an opening diameter of 90 mm and a depth of 36 mm was molded. A molded product for 20 shots is inspected, and the upper limit temperature at which the lens-shaped thickness unevenness, so-called rain drop phenomenon, on the sheet surface starts to occur in the molded product of 5% or more is A ° C. ) Is 5%
The lower limit temperature at which the above began to occur was B ° C., and each characteristic was evaluated according to the following criteria.

Criteria for Evaluation of Low-Temperature Formability A relative comparison was made based on the ratio (B / VSP) between the temperature at which the molding defect began to occur: B ° C. and the VSP of the resin constituting the sheet. The lower the value of (B / VSP), the better the low-temperature moldability.

◎: (B / VSP) is less than 1.15 ○: 〃 1.15 or more, less than 1.20 ... Acceptable level △: 〃 1.20 or more, less than 1.25 ×: 〃 1.25 or more Molding temperature range evaluation criteria Difference between A ° C and B ° C [A- B] The evaluation was made based on the following criteria.

◎: Molding temperature range of 20 ° C or higher ○: 〃 15 ° C or higher, lower than 20 ° C ... Acceptable level △: 〃 10 ° C or higher, lower than 15 ° C ×: 未 満 Lower than 10 ° C [Corner thickness /
[Thickness of the original sheet] was used as a scale of uneven thickness of the molded article, and evaluated according to the following criteria.

◎: [corner part thickness / original sheet thickness] is 0.3 or more ○: 〃 is 0.25 or more, less than 0.3 ... Acceptable level △: 〃 is 0.2 or more, less than 0.25 × 〃 is less than 0.2 7) High-speed moldability is determined by the following method evaluated.

The test sheet was heated using a contact heating type air pressure molding machine at the maximum temperature at which raindrops did not occur on the molded product (at intervals of 5 ° C, fractions were cut off), and the heating time was 0.5 to 2.5 seconds. Molded in the same manner as The shortest heating time at which the mold defect (corner portion R> 4 mm) was 5% or less was used as a measure of high-speed moldability and evaluated according to the following criteria.

◎: The shortest heating time was less than 1.5 seconds. ○: 〃 1.5 seconds or more, less than 2.0 seconds ... Acceptable level ×: 〃 2.0 seconds or more 8) Deep drawability was evaluated by the following method.

Using a contact heating type pressure air molding machine, the test sheet was used at the maximum temperature at which raindrops did not occur on the molded product (at intervals of 5 ° C, fractions were cut off), the opening diameter was 90 mm, and the depth was 36 to 72.
mm (formed at 4.5mm intervals)
Molded under the same conditions as in 6). Insufficient mold definition (R> 4 mm at corners), whitening and tearing of the molded container at each drawing depth were inspected for defects, and the maximum drawing depth at which defective products were 5% or less was evaluated based on the following criteria.

◎: Maximum drawing depth of 72 mm or more ○: 〃 63 mm or more, less than 72 mm ... Acceptable level △: 〃 49.5 mm or more, less than 63 mm ×: 未 満 Less than 49.5 mm Example 1 Styrene and α-methylstyrene as styrene components Butyl acrylate as a carboxylic acid component,
Ethyl acrylate, 2-ethylhexylate, and zinc acrylate were selected, respectively, and diluted with ethylbenzene and other appropriate solvents to obtain a copolymer (A) by thermal radical polymerization. The characteristics of this product are shown in Table 1.

A block copolymer (B) was obtained from styrene and a conjugated diene as shown in Table 2 below. In the polymerization method, butyllithium was used as a polymerization initiator in n-hexane, and the above-mentioned non-linear block polymer subjected to the coupling polymerization was obtained by a known method.

The above-mentioned method of blending the copolymer (A) and the block copolymer (B) involves dry-blending both at a desired mixing ratio, and then having a kneading mixing head, and [L / D
= 46] and melt-mixed with an extruder having a screw having a diameter of 65 mm to obtain pellets. These pellets were melted by an extruder having a screw having a diameter of 50 mm, and extruded from a T-die.
After quenching, the sheet is stretched in the sheet flow direction (vertical direction) by the speed difference of the roll group heated to the temperature conditions shown in Table 3 and then perpendicular to the sheet flow direction by a tenter under the temperature conditions shown in Table 3. The sheet was stretched in the direction (transverse direction) to obtain a sheet having a thickness of 250 μm. Table 4 shows the properties of these sheets.

GPPS is a general-purpose polystyrene, and has a weight average molecular weight (Mw) of 26 × 10 ⁴ , and a weight average molecular weight / number average molecular weight (Mw).
w / Mn) = 2.2, VSP = 106 ° C., MFR = 2.2 g / 10 min.

As a result, the low-temperature, high-formability stretched sheets of the present invention in Experiments Nos. 1 to 10 all had a tensile strength at break and elongation, an elastic modulus, a bending strength (a substitute property of toughness), transparency ( HAZ
E) Excellent balance with secondary moldability. In Tables 3 and 4, in Comparative Examples, the ratio -1 is an example in which the stretching temperature is low and the ORS is too high. Unlike the low-temperature high-formability stretched sheet of the present invention, the secondary formability of the obtained sheet is inferior. I have. The ratio -2 is a blank made of only the styrene-butadiene block copolymer (B) and has excellent bending strength but low tensile modulus,
Also, low-temperature moldability and deep drawability are slightly inferior. The ratio -3 is a blank made of only GPPS, and is inferior in bending strength and secondary moldability. As described above, only the low-temperature high-formability stretched sheet of the present invention gave satisfactory results in all physical properties and secondary moldability.

Example 2 A film was formed in the same manner as in Example 1 using the copolymer (A), the block copolymer (B), and the styrene-based polymer (C) in the combinations shown in Table 5, and the film was formed as shown in Table 6. A sheet of properties was obtained.

In this case, as the styrene polymer (C), a commercially available GPPS, AS, or MS resin having the following characteristics was used.

● GPPS stands for general-purpose polystyrene, and has a weight average molecular weight (Mw) of 26 × 10 ⁴ , weight average molecular weight / number average molecular weight (Mw /
Mn) = 2.2, VSP = 106 ° C., MFR = 2.2 g / 10 min.

● AS stands for styrene-acrylonitrile copolymer with a styrene content of 75% by weight, acrylonitrile 25% by weight,
P = 109 ° C., MFR = 4.3 g / 10 min.

MS is a styrene-methyl methacrylate copolymer having 70% by weight of styrene, 30% by weight of methyl methacrylate, VSP = 108 ° C., and MFR = 3.5 g / 10 minutes.

From the results shown in Table 6, the compositions of Experiments Nos. 11 to 18, which are low-temperature, high-formability stretched sheets of the present invention, all have good physical properties and secondary moldability, and properties that cannot be obtained with other compositions. belongs to. In Table 5, the ratio -4 of the comparative example is a blank made of only the copolymer (A), which is excellent in rigidity and transparency and relatively good in secondary moldability, but inferior in bending strength and brittle. Only molded products can be obtained. Ratios -5, 6, and 7 are examples that do not include the copolymer (A) of the present application. Ratio -5, 7
However, high-speed formability and deep-drawing formability are significantly inferior, and the level of bending strength is not sufficient. The ratio -6, in which the amount of the block copolymer (B) is increased, is lower than the practical level because the tensile modulus (the rigidity of the sheet) and the transparency are deteriorated, although these improvements have been made to some extent. Further, in this product, generation of a lot of gel was observed at the time of melt extrusion.

The ratio -8 is an example using a styrene-methacrylic acid copolymer. Since this resin has a VSP of 90 ° C. or higher, it differs from the copolymer (A) of the present invention in that secondary molding of the obtained sheet is performed. Sex is inferior. In addition, transparency and bending strength are poor.

Thus, the low-temperature high-formability stretched sheet of the present invention has characteristics that cannot be obtained with other compositions.

[Effect of the Invention] The low-temperature high-formability stretched sheet of the present invention has improved impact resistance and imparts high-speed moldability and low-temperature moldability while maintaining the optical characteristics and rigidity, which are the characteristics of the styrene resin sheet. It is a sheet.

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08L 33/00 C08L 33/00 53/00 53/00 B29K 25:00 33:00 55:00 (56) References JP-A-61-25819 (JP, A) JP-A-59-182732 (JP, A) JP-A-2-43023 (JP, A) JP-A-62-25031 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) C08J 5/18 C08L 25 / 00,33 / 00,53 / 00 B29C 55/12-55/16

Claims (2)

(57) [Claims] (1) at least one monomer selected from styrene or a styrene derivative: 97 to 20% by weight; and at least one aliphatic unsaturated carboxylic acid or a derivative thereof: 3-80. At least one copolymer (A) having a Vicat softening point of less than 90 ° C., a monomer comprising: 95 to 20% by weight, and at least one conjugated diene. And a mixture of at least one type of block copolymer (B) having at least one polymer block each consisting mainly of the above-mentioned copolymer. The heat shrinkage stress (ORS) measured according to ASTM D-1504 consisting of a resin composition having a weight mixing ratio of the union (A) and (B) of 0.05 ≦ A / (A + B) ≦ 0.99 is 2.0 to 15 kg. / cm ² and calculated from the following formula
A secondary molding sheet stretched and oriented in a biaxial direction having an ORS relaxation rate of 0.70 to 0.3. ORS relaxation rate = (ORS-2 / ORS-1) ORS-2: The sheet was immersed for 3 seconds under tension in silicon oil at 40 ° C. higher than the Vicat softening point of the resin composition constituting the sheet. ORS ORS-1 after: ORS of sheet before processing 2. At least one monomer selected from styrene or styrene-based derivatives: 97 to 20% by weight, and at least one aliphatic unsaturated carboxylic acid or a derivative thereof: 3-80. At least one copolymer (A) having a Vicat softening point of less than 90 ° C., a monomer consisting of 95 to 20% by weight, and at least one conjugated diene derivative. And a mixture of at least one block copolymer (B) having 5 to 80% by weight as a main component and forming at least one polymer block each. A resin composition in which the weight mixing ratio of the copolymers (A) and (B) is 0.05 ≦ A / (A + B) ≦ 0.99: 95 to 5% by weight; Polymers mainly composed of monomers (C): A heat-shrinkage stress (ORS) of 2.0 to 15 kg / which is measured according to ASTM D-1504 and comprises a mixed resin composition consisting of 5 to 95% by weight. cm ² ,
And the ORS relaxation rate obtained from the following equation is 0.70 to 0.32
A sheet for secondary molding stretched and oriented in the axial direction. ORS relaxation rate = (ORS-2 / ORS-1) ORS-2: The sheet was immersed for 3 seconds under tension in silicon oil at 40 ° C. higher than the Vicat softening point of the resin composition constituting the sheet. ORS ORS-1 after: ORS of sheet before processing