JPH0399846A - Stretched multilayer sheet - Google Patents

Abstract

PURPOSE:To obtain a stretched multilayer sheet having a wide molding temperature range and excellent deep drawing properties, by selecting thermoplastic resins so that the Vicat softening point of the resin constituting surface layers and the Vicat softening point of the resin constituting an inner layer are in a specified ratio, and arranging the resins in layers so that the total thickness of the surface layers has a specified proportion based on the total thickness of all layers. CONSTITUTION:A stretched multilayer sheets has surface layers and one or more inner layers, wherein a thermoplastic resin A constituting the surface layers and a thermoplastic resin B constituting the inner layers are so selected that the Vicat softening point (Va: deg.C) of the resin A and the Vicat softening point (Vb: deg.C) of the resin B have a ratio Va/Vb of at least 1.10, and the resins are arranged in layers so that the total thickness of the surface layers is 5-70% based on the total thickness of all of the layers. When the Vicat softening temperature ratio Va/Vb is less than 1.10, no improving effects can be obtained on the molding temperature range for the sheet, deep drawing properties of the sheet or on nonuniformity in the material thickness of molded products. When the percentage of the total thickness of the surface layers is less than 5%, the molding temperature range for the sheet is not broadened because the upper limit of the molding temperature is not raised sufficiently, as compared with that of a sheet of the resin constituting the inner layers. When the percentage exceeds 70%, the upper limit of the molding temperature remain unchanged and, rather, the lower limit of the molding temperature is raised, resulting in a narrower molding temperature range.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a stretched multilayer sheet made of a novel resin containing styrene as a main component, an allyl resin, a polycarbonate resin, or the like.

More specifically, the present invention provides transparency and rigidity that can be formed by means such as vacuum forming, pressure forming, and blow molding, and can be suitably used for packaging lightweight food packaging containers, other articles, and any other wide range of applications. , excellent strength, formability, etc.
This invention relates to a stretched multilayer sheet.

(Prior art) Biaxially oriented polystyrene sheets are known for their transparency, gloss,
Due to its excellent rigidity, it is used in lightweight containers for food packaging.

For forming these containers, for example, a hot plate air pressure forming method in which a sheet is brought into contact with a hot plate is usually used. However, in this method, the hot plate temperature at which the two-wheeled stretched polystyrene sheet can be formed is within a narrow range.

That is, when the hot plate temperature is high, the sheet tends to stick to the hot plate, resulting in poor development called raindrops (irregularities on the surface of the molded product). On the other hand, when the hot plate temperature is low, the sheet is not stretched sufficiently, and as a result, the molded product does not accurately reproduce the shape of the mold, so-called poor mold reproducibility occurs, and the molded product The unevenness of the meat also gets worse.

Because of these two adverse phenomena, the hot plate temperature at which biaxially oriented polystyrene sheets can be formed is limited to a narrow range.

For this reason, deep drawing is also difficult.

Further, even when heat forming is performed in a non-contact manner using another method such as infrared rays or a heating medium, conventionally, the thickness unevenness increases as the print ratio increases.

Therefore, as a method to prevent the former raindrop from occurring,
For example, JP-A-57-193321 proposes a two-wheel stretched sheet in which a diene rubber-modified polystyrene film is laminated on a styrene sheet. Also, JP-A-5
No. 8-98222 proposes a biaxially stretched sheet in which a skin layer containing an inorganic substance is laminated on a styrene sheet.

However, in these methods, the surface of the polystyrene sheet is roughened to allow air to escape and prevent raindrops. For this reason, it is difficult to obtain molded products with excellent transparency.

Furthermore, as a method for improving the latter mold reproducibility, for example, Japanese Patent Application Laid-Open No. 55-144158 proposes a biaxially stretched sheet in which a polyolefin resin is laminated as a skin layer on a styrene sheet.

However, in this method, a polyolefin resin with poor transparency and rigidity is used for the surface layer, so
The molded product becomes opaque and non-rigid. Furthermore, since different types of resins are laminated, an adhesive layer is required, and scraps generated during film formation and molding cannot be effectively recovered, which is disadvantageous in terms of cost.

In this way, the fact is that a stretched styrene resin sheet that has excellent rigidity, strength, and transparency for sheets and molded products, has a wide moldable temperature range, and is excellent in deep drawing has not been found to date. It is.

(Problems to be Solved by the Invention) Under these circumstances, the present invention solves the problem of styrene resin,
It maintains the transparency and rigidity that are characteristic of acrylic resins and polycarbonate resins, has a wide moldable temperature range in pressure forming and vacuum forming, has excellent deep drawability, and is cost-effective. , was made for the purpose of providing a co-stretched multilayer sheet made of the above resin.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, in a multilayer stretched sheet having a surface layer and an inner layer, the Vicat softening point (VA) of the thermoplastic resin (A) constituting at least one surface layer is
: °C) and the Vicat softening point (vt: °C) of the thermoplastic resin (B) constituting at least one other layer or inner layer, the ratio (v-/Vb) of the resin is at least 1.10. A co-stretched multilayer sheet was selected and arranged in each layer, and the total thickness of the surface layer was 5 to 70% of the total thickness.

Hereinafter, the present invention will be described in detail using a molding method using hot plate contact heating as an example of its application, but it is not limited to this application.

In the biaxially stretched multilayer sheet of the present invention, the Vicat softening point of the thermoplastic resin (A) forming at least one surface layer is higher than that of the thermoplastic resin (B) forming at least one other layer or the inner layer. ) is higher than the Vicat softening point of the resin forming at least one surface layer (Va:
"C) and the Vicat softening point (vb: °C) of the resin forming at least one other layer or inner layer (v, /
, ) is 1.10 or more, preferably 1.15 or more.

Moreover, the upper limit is 2.70 or less, preferably 2.00
It is more preferably 1.70 or less.

If this Vicat softening point ratio V, / V, is less than 1.10, the effect of improving the sheet forming temperature range, deep drawability, and uneven thickness of the molded product will not appear, which is undesirable, especially deep drawability. , from the viewpoint of highly improving molded product thickness unevenness, V, /V
It is effective to make , 1.15 or more.

Further, when V,/V, exceeds 2.70, a sheet with a wide moldable temperature range and good deep drawability can be obtained, but it is important to apply effective stretching orientation to the inner layer during sheet film formation and It becomes difficult during secondary forming, resulting in a weakened toughness (folding strength) and a brittle sheet.
Undesirable.

However, if a resin with strong toughness is selected for the inner layer even during low stretching orientation, this is not a limitation, but it is disadvantageous to expect a further improvement in rigidity imparted as a synergistic effect.

Next, in the present invention, the thermoplastic resin (A) constituting the surface layer is at least one monomer selected from styrenic resins containing styrene or styrene derivatives as a main component, aliphatic unsaturated carboxylic acids, and derivatives thereof. The Vicat softening point is 100 to 100 and is mainly made of resin selected from acrylic resin, polycarbonate resin, etc.
The temperature of the resin is 160°C, preferably 105 to 150°C. These resins may be used alone or in combination and mixed.

The above-mentioned styrene resin containing styrene or a styrene derivative as a main component is, for example; (1) general purpose polystyrene;

(2) Alkyl-substituted styrene polymers such as α-methylstyrene, and copolymers of these monomers and styrene.

■ High-impact polystyrene with a small amount of rubber.

(2) A styrene-conjugated diene block copolymer containing 95 to 70% by weight of styrene.

■ Can be copolymerized with styrene and/or alkyl-substituted styrenes containing 50% by weight or more, preferably 60% by weight or more of one or more selected from styrene components and alkyl-substituted styrenic resins. Copolymers with monomers or intramolecular or intermolecular reactants of these.

These may be used alone or in combination of two or more.

In addition, examples of monomers copolymerizable with styrene and/or α-methylstyrene include acrylic acid and/or
or its esters, methacrylic acid and/or its esters, maleic anhydride, maleimide, acrylonitrile, and the like. These copolymerizable monomers may be used alone or in combination of two or more.

In the present invention, the acrylic resin containing at least one monomer selected from aliphatic carboxylic acids and their derivatives as a main component includes, for example; At least one selected from acrylic monomers such as esters [! A resin consisting of monomers and their intramolecular reactants.

■ Above 1. The total amount of one or more selected acrylic monomer components is 50% by weight or more, preferably,
A copolymer of the acrylic monomer and a copolymerizable monomer containing 60% by weight or more.

etc. These may be used alone or in combination of two or more.

Examples of monomers copolymerizable with the acrylic monomer include styrene, alkyl-substituted styrenes such as α-methylstyrene, maleic anhydride, maleimide, acrylonitrile, and the like.

One type of these copolymerizable monomers may be used, or
Two or more types may be combined.

The polycarbonate resin referred to in the present invention is, for example, an aromatic dihydroxy compound made rigid by a known transesterification method, phosgene reaction, solvent method, or the like.

As the aromatic dihydroxy compound, 2.2-(
4,4-bishydroxyphenyl)propane is particularly preferred, and furthermore, these dihydro compounds and diols,
It may be copolymerized with a dibasic acid, diamine, etc. by a known method.

Further, the surface layer resin may contain a mold release agent, a heat stabilizer, a lubricant, an antistatic agent, an ultraviolet absorber, a plasticizer, an oligomer, and other commonly used additives, if necessary.

Next, in the present invention, the thermoplastic resin (B) constituting at least one other layer other than the surface layer or the inner layer is a styrenic resin containing styrene or a styrene derivative as a main component, a styrene or a styrene derivative and a conjugated diene or a Vicat softening resin mainly composed of a copolymer with a conjugated diene derivative, a copolymer of styrene or a styrene derivative, an aliphatic unsaturated carboxylic acid, and at least one monomer selected from the derivatives, etc. Point is 60~140°
It is a resin of C.

The styrenic resin containing styrene or a styrene derivative as a main component is, for example, general polystyrene, polyalkyl-substituted styrenes such as polyα-methylstyrene, or a combination of styrene monomer and alkyl-substituted styrene monomer. A polymer.

Furthermore, a copolymer of styrene or a styrene derivative and a conjugated diene or a conjugated diene derivative is, for example, a block copolymer composed of at least one unit composed of styrene or alkyl-substituted styrene and at least one unit composed of a conjugated diene. , or a copolymer in which 80% or more of the double bonds derived from the conjugated diene are saturated, and further, for example, a modified version of these with a known monomer having a carboxylic acid group such as maleic anhydride. The styrene component of these resins is 95 to 70% by weight,
The conjugated diene component used is 5 to 30% by weight. Examples of the conjugated diene component include butadiene, isoprene, and the like.

Furthermore, the copolymer of the above-mentioned styrene or styrene derivative and at least one monomer selected from aliphatic unsaturated carboxylic acids and the derivatives is, for example, a copolymer in which the total amount of styrene and/or alkyl-substituted styrene components is 50% by weight. that's all,
Preferably, it is a copolymer containing 60% by weight or more.

In addition, other monomers to be copolymerized include methacrylic acid and/or
or its esters, acrylic acid and/or its esters, maleic anhydride, acrylonitrile, and the like. Preferred examples of the above esters include esters with C1 to C alcohols, such as propyl, butyl, pentyl, hexyl, octyl, etc. For example, styrene and butyl acrylate in a concentration of 2 to 18% by weight. The Vicat softening point of the copolymerized material is controlled at 71-74°C.

These monomers may be used alone or in combination of two or more. Furthermore, these copolymers may be subjected to an intramolecular reaction such as an intramolecular dehydration reaction or an intramolecular dealcoholization reaction. good.

The above resins may be used alone or in combination of two or more. Furthermore, additives such as plasticizers, oligomers, and other polymers may be added to adjust the Vicat softening point. If necessary, a resin adhesive to the surface layer, a recovered polymer, a stabilizer, and other commonly used additives may be included.

Furthermore, in order to further improve the toughness and moldability of the stretched motorcycle sheet of the present invention, a styrene-conjugated diene block copolymer and/or a hydrogenated product of the copolymer, etc. are mixed into the thermoplastic resin. You may do so. Furthermore, a layer made of these copolymers may be added to the inner layer.

The styrene-conjugated diene block copolymer is a block copolymer composed of at least one unit consisting of styrene and at least one unit consisting of a conjugated diene, in which the styrene component is 50 to 80% by weight and the conjugated diene component is 50 to 80% by weight. Examples include those containing 20 to 50% by weight of components.

Further, the styrene-conjugated diene block copolymer hydrogenated product is a copolymer composed of the same units as the above-mentioned styrene-conjugated diene block copolymer, and contains 20 to 60% by weight of the styrene component and conjugated diene block copolymer. Ingredients are 40~
80% by weight and 80% or more of the double bonds derived from the conjugated diene are saturated. Further, examples of the conjugated diene component include butadiene, isoprene, and the like. Furthermore, for example, these may be modified with a known monomer having a carboxylic acid group such as maleic anhydride.

These copolymer resins can be mixed into both the inner layer and the surface layer. However, from the viewpoint of maintaining rigidity and transparency, the addition to the surface layer should be 15% or less, more preferably 10%
% or less.

On the other hand, the above-mentioned copolymer resin can be added as desired since the addition of the copolymer resin to the inner layer causes little deterioration in rigidity and transparency. Therefore, it is more preferable to mix the copolymer resin into the inner layer.

In the stretched multilayer sheet of the present invention lacking one layer, the thickness ratio of the image surface layer needs to be 5 to 70% of the total thickness.

If this thickness ratio is less than 5%, the upper limit of the moldable temperature (maximum hot plate temperature at which raindrops do not occur) will not rise sufficiently compared to the resin sheet constituting the inner layer, and as a result, the moldable temperature range will not be expanded. Moreover, even if it exceeds 70%, the upper limit of the moldable temperature does not change, but on the contrary, the lower limit of the moldable temperature increases, and the temperature range becomes narrower, which is not preferable.

In addition, as a secondary effect of the present invention, by keeping the image surface layer within the above range, a synergistic effect of each layer works during sheet film formation and molding, resulting in excellent rigidity and toughness (folding strength). , sheets, and molded products are obtained.

From the viewpoint of expressing this synergistic effect, the thickness ratio of the image surface layer is preferably 5 to 50%, more preferably 10 to 4%.
It is more effective to set it to 0%.

Further, without departing from the gist of the present invention, in addition to at least one layer made of a resin whose Vicat softening point is 1/1.10 times or less of the Vicat softening point of the surface layer resin, the inner layer may include at least one layer, for example, a recovered polymer layer. , an adhesive layer, another styrene resin layer whose Vicat softening point does not exceed that of the surface layer resin, etc. may be included, or in some cases, a resin layer similar to the surface layer does not exceed 173 of the total inner layer, and the surface layer may be included within the layer composition ratio.

In addition, in the stretched multilayer sheet of the present invention, the arrangement of each layer may be, for example, a resin layer with a Vicat softening point of v and °C, and a resin layer with a Vicat softening point of Vb'c with b (V
a/Vh≧1.10), a/b, a
/ b / a, a / b / a / b /
There are a, a /b/a/b/a b/a, etc.

In addition, when the other resin layer (referred to as C) is added to the inner layer, the arrangement pattern is, for example, a/c/
b, a/b/c/b/aSa/c/b/c/a, a/b
/c/a/c/b/a.

··and so on. However, the present invention is not limited to the above examples as long as the characteristics of the multilayer sheet of the present invention are not affected.

In the present invention, the surface layer, in the case of a two-layer sheet, refers to the layer on the side that contacts the hot plate during molding. In the case of a sheet with three or more layers, it refers to both the front and back outermost layers.

Furthermore, in the case of a two-layer sheet, the inner layer refers to the layer on the side that does not contact the hot plate during molding, and in the case of a sheet with three or more layers, it refers to at least one layer other than the image surface layer.

In addition, the Vicat softening point in the present invention refers to the ASTM
This is a value measured in accordance with D-1525 (load: 1 kg, temperature increase rate: 2°C/m1n).

An example of a preferable combination is when the surface layer resin (A) is mainly composed of polystyrene resin (Vicat softening point -104 to
108°C), at least lN multilayer or inner layer resin (B
) is a styrene-butadiene block copolymer with a softening point of 80 to 9 B'C) alone, or these are 5
~30% by weight, when mixed with the above surface layer resin, the above-mentioned styrene and acrylic ester (propyl and butyl alcohols as alcohol components) are 95:5 to 7.
This is a case where a polymer copolymerized at a ratio of 0:30 (each % by weight) is used alone or mixed with the above-mentioned polystyrene resin, styrene-butadiene block polymer, etc. in an arbitrary range.

In addition, when the surface layer resin (A) is the above-mentioned styrene-based heat-resistant resin (Vicat softening point is 110 to 150"C), the inner layer is the same as above, and the polystyrene-based resin V, /V, is 1.10 The heat-resistant resin may be arbitrarily selected from the heat-resistant resins alone or blends selected as described above, but the present invention is not limited to these.

The stretched multilayer sheet of the present invention may be a uniaxially stretched sheet as long as it does not become brittle depending on the resin selection conditions, but preferably a biaxially stretched sheet. In both cases, if they are not similarly brittle, the main orientation may be set in the surface layer, and the weak orientation may be set in the inner layer and other layers, thereby greatly improving the secondary formability.

In the present invention, when a mixture of two or more resins is used in the surface layer and/or the inner layer, and/or oligomers, mold release agents, stabilizers, plasticizers, and other agents are used. When adding additives such as, it may be used as a tri-blend, or it may be used as pellets after preliminary kneading with an extruder, Banbury mixer, co-kneader, etc.

There are no particular limitations on the method for producing the two-wheel stretched multilayer sheet of the present invention, and a multilayer sheet may be created by a method conventionally used in the production of two-wheel stretched multilayer sheets, such as coextrusion, and then biaxially stretched sequentially or simultaneously. A method of melt extruding a sheet, laminating it with another sheet while it is still in a high temperature state to create a multilayer sheet, and similarly stretching this with two wheels, or a method of laminating the stretched sheet of the present invention to another sheet. It is possible to adopt methods such as

Further, methods for biaxial stretching include generally known tenter methods and inflation methods.

These stretching ratios are 1.5 in at least one direction.
The stretching temperature is usually 8 times, preferably 2 to 6 times. Point Mo10) to (Vicat softening point of surface layer resin +40) "C" is selected.

The biaxially stretched multilayer sheet of the present invention has a total thickness of 0.01
mm ~1.0mm, preferably 0.03~0.5mm
within the range of

In addition, heat shrinkage stress measured according to ASTM D-1504 (temperature, Vicat softening point of surface resin + 30°C,
The peak stress value under heat medium silicone oil conditions is usually 2 to 2.
18 kg/cd, preferably in the range of 3 to 13 kg/cj is suitable. The heat shrinkage stress is 2kg/C
If it is less than Ii, the orientation level is too low and there is a risk of cracking during punching of the molded product, and if it exceeds 18 kg/d, a general molding machine will not only produce molded products with poor mold reproducibility, but also cause excessive orientation. This is not preferable as it may cause more whitening and cracking of the molded product.

(Example) Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these in any way.

In addition, each characteristic was evaluated according to the following method.

■ The Vicat softening point of the surface resin of the test sheet + (15~
55))" C1 heating time 3.0 seconds, molding time 1.5 seconds,
It was molded into a cylindrical molded body with an opening diameter of 100 mm and a depth of 20 mm under conditions of a molding pressure of 3 kg/cd. After inspecting 50 shots of molded products, the hot plate temperature at which raindrops begin to occur in molded products of 5% or more is A"C2.The hot plate temperature at which molding defects of molded products are less than 5% is B"C. Toshi, (A-B)”
The moldable temperature range was determined using C and evaluated according to the following symbols.

The test sheet was heated using a contact heating pressure air forming machine at a hot plate temperature [Vicat softening point of the surface resin of the test sheet + 35].
A cylindrical molded product with an opening diameter of 100mm and a depth of 40 to 70mm was formed under the conditions of ``C1 heating time 5.0 seconds, molding time 2゜q seconds, and molding pressure 5 kg/cd.The molded product for 50 shots was formed. The molded product was inspected, and the maximum drawing depth at which the molded product had no whitening or tearing, and the wall and bottom surfaces were 95% or more, was determined and rated according to the following symbols.

The test sheet was heated using a contact heating type pressure forming machine at a hot plate temperature [Vicat softening point of the surface resin of the test sheet + 30]°C.
, heating time 3.0 seconds, molding time 2°0 seconds, molding pressure 5
kg/c- condition, opening diameter 100mm, depth 20
It was molded into a cylindrical molded body of mm. Measure the corner thickness of the wall and bottom of the molded product for 10 shots with a micro gauge (minimum scale 0.001 mm) at 5 points per each molded product), [average value of corner thickness] / [original The average value of the sheet thickness] was determined and evaluated according to the following symbols.

The original sheet thickness was calculated from the weight per unformed sheet/mmt (average of n·10).

■ ■ Using a contact heating type air pressure forming machine, the standing test sheet was heated at a hot plate temperature [Vicat softening point of the surface resin of the test sheet + 303
"C5 heating time 3.0 seconds, molding time 1°5 seconds, molding pressure 3 kg/cd, opening diameter 90 mm, bottom diameter 8
It was molded into a pudding cup-shaped molded product with a diameter of 0 mm and a depth of 20 mm. The front part of the bottom of this molded product was compressed at a speed of 300 mm/min at 23'C and 65% RH, and the molded product was compressed to a length of 5 m.
Measure the force when compressed (average of n-5), Tkg
And so.

In addition, a commercially available polystyrene biaxially oriented sheet of the same thickness (
The Styro Sheet "3000" made by Fukaisei was measured in the same way.
/S was determined and evaluated according to the following symbols.

Measured in accordance with ASTM D~2176 (bending angle, 135 degrees left and right from the center, load 1 kg) (average value of n=10), and evaluated according to the following symbols.

Note that this folding strength is a substitute characteristic for improving the brittleness of the sheet, and the greater the number of folding cycles, the better the toughness.

■ 14u1 STM Haze value in accordance with 1003 measure (average of n=5), Graded according to the following symbols did.

Also, The resins shown in Table 1 were used.

Table 1 *vsp: Vicat softening point (according to ASTM D-1525) R,, R, = Me or Hl Intramolecular dehydration reaction between adjacent acrylic acid units, or intramolecular dehydration reaction between adjacent acrylic acid units and methyl methacrylate units Suminari due to dealcoholization reaction.

(Example 1, Comparative Example 1) A three-layer T-die was attached to a coextruder having screws of 65 mm diameter and 40 mm diameter, and the surface layer resin shown in Table 2 was supplied to the 40 mm diameter extruder. The inner layer resin shown in Table 2 was supplied to an extruder with a diameter of 1.5 mm, and the inner layer resin was melt-extruded and stretched 2.5 times lengthwise by the speed difference between the roll groups heated to (Vicat softening point of the surface layer resin + 15°C). and then laterally stretched with a tenter ([Vicat softening point of surface resin + 2
53'C13,3 times), and the composition ratio of each layer was 10
/80/10 multilayer sheet was obtained (sheet thickness 0.25
mm).

These sheets were evaluated for their moldable temperature range, deep drawability, and uneven thickness of the molded product. The results are shown in Table 2 (Example 1; Experimental numbers 1 to 7; Comparative example 1; Experimental numbers 8 to 12).

From Table 2, it can be seen that only biaxially stretched multilayer sheets with V, /V of 1.1 or more are excellent in moldable temperature range, deep drawability, and uneven thickness of molded products.

Table 2 Inner Layer Resin Tototsu 1 Coupling 1 ω Tortoise (Example 2, Comparative Example 2) Using the resins shown in Table 3, sheets with the layer configurations shown in Table 3 were created in the same manner as in Example 1. (Sheet thickness; 0.2
1mm). At this time, the roll temperature in the longitudinal stretching section was set to [Vicat softening point of the surface layer resin + 18], and the C1 stretching ratio was set to 2.7.
It was doubled. Further, the tenter temperature was set to [Vicat softening point of the surface layer resin +30]°C, and the stretching ratio was set to 3.7 times.

The moldable temperature range, deep drawability, uneven thickness of the molded product, rigidity, bending strength, and transparency of these sheets were evaluated.

The results are shown in Table 3 (Example 2; Experiment No. 13-1
5.17-19 and 21-23, Comparative Example 2; Experiment No. 1
6.20 and 24).

(Comparative Example 3) A single-layer T-die was attached to an extruder having a screw diameter of 50 mm, and each resin shown in Table 4 was melt-extruded and stretched to form a film under the same conditions as in Example 2. The moldable temperature range, deep drawability, uneven thickness of the molded product, rigidity, bending strength, and transparency of the obtained sheet were evaluated.

The results are shown in Table 4.

From Tables 3 and 4, it is clear that the two-wheel stretched multilayer sheet of the present invention has a flow rate, a moldable temperature range, deep drawability, uneven thickness of the molded product, rigidity,
It can be seen that the folding strength and transparency are excellent.

On the other hand, it is difficult to balance these factors when the surface layer is too thick (Comparative Example 2) or in a single layer sheet (Comparative Example 3).

Table 3 (Example 2 and Comparative Example 2) Table 4 (Effects of the invention) The stretched multilayer sheet of the present invention is: (1) A thermoplastic resin with a relatively high Vicat softening point is used as the surface layer resin, and the inner layer The resin used is a thermoplastic resin with a relatively low Vicat softening point that has better fluidity than the surface layer, so it has an excellent balance of raindrop resistance and reproducibility, resulting in a wide temperature range. In addition, molded products with excellent deep drawability and less uneven thickness can be obtained.

(2) Since the combination of the surface layer and the inner layer has a synergistic effect during stretching and molding, it is possible to obtain sheets and molded products with particularly excellent rigidity and toughness, and it is also possible to make the sheets thinner.

(3) The above modifications (1) and (2) are possible without impairing the properties of polystyrene-based, acrylic-based polycarbonate-based stretched sheets such as transparency and gloss.

(4) In the stretched sheet of the present invention, scraps of the sheet remaining during punching of the molded product may be added to the inner layer, if necessary. In this case, deterioration in transparency can be minimized and scrap polymer can be effectively recovered.

It has the following characteristics and has extremely high industrial value.

As described above, the multilayer sheet of the present invention has excellent transparency, rigidity, and toughness, has a wide moldable temperature range, and has excellent deep drawability and uneven thickness of molded products, so it can be used for lightweight food packaging containers. It is suitably used as a sheet for molding containers and other containers.

(1 other person)

Claims (1)

[Claims] In a multilayer stretched sheet having a surface layer and an inner layer, the Vicat softening point (V_a: °C) of the thermoplastic resin (A) constituting at least one surface layer and at least one other layer or inner layer Vicat softening point of thermoplastic resin (B) (
The resin whose ratio [V_a/V_b] is at least 1.10 is selected and arranged in each layer, and the total thickness ratio of the surface layer is 5 to 70% of all the layers. A co-stretched multilayer sheet characterized by: