JPS61159442A - Shrinkable styrene resin film - Google Patents

Abstract

PURPOSE:The title film excellent in environmental stress cracking resistance, blocking resistance, etc., obtained from a mixture comprising a styrene/butadiene block copolymer, two specified antioxidants, erucamide, an inorganic fiber, etc. CONSTITUTION:A styrene/butadiene block copolymer having a styrene content of 60-90wt%, a nonblock content <=15% and a number-average MW of 20,000-500,000 is mixed with 0.1-1.5wt% antioxidant selected from group A consisting of 2,2'-methylenebis(4-methyl-6-t-butylphenyl), 2,6-di-tert-butyl-4- methylphenol, etc., and 0.1-1.5wt% antioxidant selected from group B consisting of 4,4'-thiobis(3-methyl-6-t-butylphenol), 2-mercaptobenzimidazole, etc., 0.05-0.5wt% erucamide of an impirity content <=20wt%, 0.05-0.5wt% erucamide of an impurities content <=20wt%, 0.05-0.5% inorganic filler such as silica and/or 0.1-1.5% high-impact polystyrene.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a shrink film made of a styrene-butadiene block copolymer.

(Prior Art) In recent years, uniaxially stretched films based on styrene-butadiene block copolymers (hereinafter referred to simply as S-B copolymers) have been used as shrink labels for glass and plastic containers due to their excellent transparency and hygienic properties. As a film for Tokukai Sho! ;g-4'1
No. 050 etc. have been proposed.

(Problems to be Solved by the Invention) However, the uniaxially stretched film of the S-B copolymer is susceptible to so-called environmental stress cracking, in which the film cracks due to external environmental conditions after being heat-shrink coated on a container or the like.

In order to solve this problem, technologies such as blending two types of S-B copolymers (JP-A-Sho Kg-22!rleA) have been proposed, but the environmental stress cracking resistance is still poor. I was not satisfied.

(Means for Solving the Problems) The present invention aims to further improve the environmental stress cracking resistance of the conventional S-B copolymer film, and its gist is that the styrene content is 60%. ~90% by weight block copolymer of styrene and butadiene, (1) at least one antioxidant selected from each of the following groups (A) and (B) (2) erucic acid amide and (3) a styrenic resin shrink film containing an inorganic filler and/or high impact polystyrene.

Group (A) coated t-butyl-ta-(,7'-t-
Butyl-5'-methyl-'-hydroxybenzyl)-
termethylphenylacrylate, y, y'-methylene-bis-(a-methyl-A-t-butylphenyl), 6-di-t-7'' thyl termethyl-phenol 1, octadecyl, y-(3, s-
di-t-butyl-l-hydroxyphenol) flobionate (B) group 6, (41-thio-bis-(J-methyl A- to monobutylphenol), -monomercabutobenzimidazole, 2,4!-bis (n-octylthio)-b
-(a-hydroxy-3,5-di-t-butylanilino) -t, 3. S.

-triazine, triethylene glycol bis-J -(
,? -t-butyl-teihydroxy-5methyl-phenyl)propionate, 2'-thiodiethylbis-[
3-(3,5-di-t-butyluda-hydroxyphenyl)-flobio, +-)],]distearylupentaerythritol di-phosphite, t,t,J-)lis(2-methyluda-cytolyso) norphosphite-5-
t-butylphenyl)butane, tert-butylidene bis(3-methyl-ru) t-7
"Tylphenyl-di-tridecyl) phosphite, bis[comethyl-e-(J-n-tridecylthiopropionyloxy)-S-t-butylphenyl] phosphite."

That is, as a result of extensive research on the effects of various additives on the environmental stress cracking resistance of S-B copolymers, it was found that group A of the antioxidants mentioned above has a particularly effective effect on the appearance of extrusion.
It has been discovered that the group has an extremely excellent effect on preventing film deterioration after film formation, and that these factors combine to improve environmental stress cracking resistance. moreover.

The addition of these antioxidants increases the amount added in combination with other additives, especially lubricants, etc., and bleed is likely to occur. Alternatively, by adding high impact polystyrene in combination, bleeding could be prevented without impairing blocking resistance.

In the following explanation, unless otherwise specified,
It shall be expressed in weight percent.

In the film of the present invention, the main component resin is the above-mentioned JP-A Showa JTG-'I10! ; A styrene-butadiene block copolymer (hereinafter abbreviated as SB copolymer) disclosed in Publication No. 0 is used. That is, this S-B
The copolymer has a heavy twill ratio of styrene and butadiene of AO:'
70-9ri:S, preferably 70:30-qo:to,
More preferably 75:2! ;-g! :Ir,
The number average molecular weight of the styrene block is preferably 70.0
00~kooo, ooo, more preferably Koθ, O
θθ~s o, o o o. This copolymer has at least one, preferably one or more, styrene block and at least seven butadiene blocks. Here, butadiene block refers to polybutadiene block or butadiene containing 50% or more, preferably 70%
As described above, a polymer block containing 9θ or more is more preferable, and examples of copolymerized monomers that this polymer block may contain include styrene, isoprene, and the like.

In addition, the non-blocking rate of this S-B copolymer expressed by the following formula is preferably less than 1S, preferably less than 0%, more preferably less than 5%, and depending on the purpose, it may exceed 0%. Good too.

The above-mentioned S-B copolymer is disclosed in the above-mentioned JP-A-5R-aior.

Manufactured according to the method described in the publication.

General formula (a) (s-s included (n-J~to) (b) S+B-8 included (n-u~
l O) (c) B+S-8 (n-co~lO)) [(B-8 large → iTx (Bxj~10゜thick l+
+l0) (E)C(s-B+-86lowX(HR-/~10゜
gM/S-/(7) (In the above formula, S is a styrene block, B is a butadiene block, and X is a residue of a coupling agent or a residue of a polymerization initiator of a polyfunctional organolithium compound), etc. It is obtained as a linear block copolymer or a radial block copolymer represented by

Melt 7 measured according to JIS KAt7θ
e+-(200℃, 5-weighting) is Q, 1~! rOf//
Q portion is suitable.

The number average molecular weight of the butadiene block of this S-R copolymer is not particularly limited, but it is preferably 200 to 60,000, and the number average molecular weight of the S-B copolymer itself is ko, ooo - It is preferable that zoo, oθ0. Further, to the extent that the basic properties of the copolymer are not impaired, functionalities such as hydroxyl groups, thiol groups, sulfonic acid groups, carboxyl groups, and amine groups can be added by hydrogenation, halogenation, halogen hydrogenation, epoxidation, or chemical reaction with ff1K. It may also be one with a group introduced therein. Furthermore, a general-purpose styrene resin may be mixed with this copolymer to the extent that the impact strength is not reduced (30% or less).

The film of the present invention uses the above-mentioned S-B copolymer as a base material, and the above-mentioned antioxidant is added thereto as a first component.

The amount of the group A antioxidant added is preferably o, t-t, s%, and the amount of the group B antioxidant added is preferably 0.1-7.5%. Group A antioxidant is 0. / If it is less than %, the extrusion appearance will deteriorate,
If the amount of group B antioxidant is less than 0.1%, the environmental stress cracking resistance will be poor. Also, both A and B groups are installed.
, S% is undesirable as bleeding occurs.

Next, erucic acid amide imparts a slipping effect to the film after film formation, and has particularly excellent effects on printability and solvent sealability. Stretched films produced by blending fatty acid amides other than erucic acid amide have the disadvantage that the ink is likely to peel off after printing, and the sealing strength is weak when solvent sealed. Since erucic acid amide is usually made from rapeseed oil, commercially available erucic acid amide contains impurities with the following carbon numbers:
Fatty acid amide of less than 10% may be mixed in as an impurity, but as long as this impurity is less than 0% in weight, there is no particular problem and it can be used in the present invention. If the impurity content exceeds 20% by weight, the printability and solvent sealability will deteriorate, which is undesirable.

In the present invention, the amount of erucic acid amide is usually S-B
It is best to have a weight ratio of o, o, t - o, s relative to the copolymer; if it is too small, the sliding effect will be insufficient, and if it is too large, bleeding will increase, improving printability and solvent sealability. becomes worse.

The additive may be added to the above sn copolymer at any time from the time of polymerization to the time of melt film formation, but it is preferable to add it before manufacturing the polymer pellet because it will be uniformly dispersed. .

As the inorganic filler, silica, calcium carbonate, magnesium carbonate, calcium sulfate, aluminum hydroxide, talc, clay, etc. are used, and fillers with a particle size of 5 μm or less are preferable because the resulting film has good gloss. The amount added is preferably in the range of 0.05 to O,S%. 0.0,
! If it is less than t%, blocking resistance is poor, and O,S
If the amount exceeds %, transparency and gloss will decrease.

In the case of utps, the amount added is 0. ／−／、! The range of r% is preferable; if it is less than o or i%, blocking resistance will be poor, and if it is more than t or s%, transparency and gloss will decrease.

In addition, additives such as ultraviolet absorbers and antistatic agents may be used in addition to the above.

The film forming and stretching method is the conventionally commonly used T-die method.
A tubular method or the like may be used, and stretching may be carried out in the longitudinal l-axis, transverse l-axis or co-axis direction depending on the intended use of the film. The stretching temperature is lower than the Vicat softening point of the resin.
c In the high temperature range, the stretching ratio is unidirectional/2 to 7.
It is sufficient to select within the range of 0 times.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example/-/U and Comparative Example 1. As a base resin, the styrene content is 7 or less, and the Vicat softening point is 9.
Using a styrene-butadiene block copolymer with an average molecular weight +oooo at 3°C, (1) one type each from Group A (A/-e) and Group B (B/-9) described below as an antioxidant. The samples were selected and added in 0.3% increments as shown in Table 1 as Examples /-/. Also, A-/, B-
Comparative Example 1, in which only one of / was added by t and s%
It was set as λ.

In both cases, (2) 0.1% erucic acid amide, (3) 0.2% inorganic filler and no-impact styrene (
Added 7.j.

The above resin composition was melt-extruded from a T-die using COOOC to a thickness of Q, 2! A sheet of 8111 was obtained, and this sheet was rolled in a tenter at an ambient temperature of /OOC in the transverse direction for 5 minutes.
The film was stretched twice to obtain an axially stretched film having a thickness of Sθμ.

The uniaxially stretched film thus obtained was evaluated for the following items, and the results are shown in Table 1.

Extrusion appearance: The original sheet after extrusion was visually observed, and those with no fish eyes over an extrusion length of 10 m were rated O, and those with fish eyes were rated ×.

Environmental stress cracking resistance: After printing the above stretched film, the circumference is 231 so that the horizontal direction is the circumferential direction.
A cylindrical label with a length of 1E1m and an axis length of 32rm was made, and it was coated on a glass bottle with a body circumference of 13wm and a shoulder height of 779M, and passed through a hot air tunnel at an ambient temperature of 200℃ for 76 seconds. Shrinked to fit. This coating was left outdoors and evaluated based on the number of days until cracks appeared in the shrink film. The larger the number of days, the better.

Blocking resistance: The shrink film was rated at 10 (M×//
After cutting into CIn, stacking 30 sheets and applying pressure to 10 f/d, and leaving it in the atmosphere of J5C for 2 weeks,
When you turn it over by hand, those that peel off in pieces are considered good, and those that do not easily peel off are considered bad.

Transparency: Measured using a commercially available haze meter, transparency was evaluated as good if the haze was 7'4 or less; transparency was evaluated as good if the haze was 7'4 or less, and × was evaluated if the haze exceeded 7 easy.

Bleed: After the film was left in a room at 30° C. for 1q months, it was rated as × if it did not leave any marks when rubbed with fingers.

Group A: A-/2-t-butyl-A-(,y'-t-butyl-5'-methyl-co'-hydroxybenzyl)-tt-
Methylphenyl acrylate A-co λ, co'-methylesine bis=(Hiro-methyl-A
-t-butylphenyl) A-32,1,-di-t-butyl-Hiro-methyl-phenol A-Hiro Octadecyl, 7- (3,s-di-monobutyl-t- and droxyphenol) Propionate 8 Group: 1ll-/ /7,4'-thio-bis-(3-methyl-1-butylphenol) B-I! -Mercaptopene diimidazole B-J
Co, q-bis(n-octylthio)-6-(guhydroxy-3,5-di-t-butylanilino) -i, 3. s -triazine B-1'lJ ethylene glycol bis-3-(, y-t
-Butyl-qhydroxy-S methyl-phenyl)propionate B-52,2'-thiodiethylbis-[3-(3,S-
di-t-butyl-tei-hydroxyphenyl)-propionate B-A distearyl-pentaerythritol-di-
Phosphite B-? /, /,, 3-tris(comethyl-goozitridecylphosphite-y-t-butylphenyl)butane B-g η, dag-tylidene bis(3-methyl-6-
t-Butylphenyl-di-tridecyl) phosphite B-9 bis[comethyl-'I-(3-n-tridecylthiopropionyloxy)-S-t-butylphenyl] phosphite As is clear from Table 1, Group A and B as antioxidants
Examples 7 to 9 were excellent in extrusion appearance, blocking resistance, and transparency, with no bleeding, and environmental stress cracking resistance was also excellent with a score of 34 on the day. Ta.

On the other hand, Comparative Example 1 lacking Group B as an antioxidant had a short environmental stress cracking resistance of 23 days, and Comparative Example λ lacking Group A had poor extrusion appearance.

implementation? I11. y, te and Comparative Example 3 to Example/
-/Using the same base resin as A-/ as an antioxidant
0.3% and B-/003% were added, and further erucic acid amide θ,
Example 13: A composition to which 13% of calcium carbonate O with an average particle size of o and gμ was added was prepared as Example 13, erucic acid amide or HIPS.

Compositions lacking both calcium carbonate were designated as Comparative Examples 3-S.

Uniaxially stretched films were obtained from these compositions in the same manner as in Example/-/2, and the extrusion appearance etc. were evaluated in the same manner as in Example/-72. The results are shown in Table 2.

As is clear from Table 1, erucic acid amide and HI
Examples /3 and /9 in which PS and inorganic filler were added had good extrusion appearance, blocking resistance, and transparency, had little bleeding, and had excellent environmental stress cracking resistance of t6 days.

On the other hand, in Comparative Examples 3 and 3, which lack erucic acid amide, the transparency deteriorates when an amount of inorganic filler required for blocking resistance is added, and as in Comparative Example 5, blocking resistance is improved only with erucic acid amide. If an attempt is made to obtain this, bleeding will occur, which is undesirable, and it is essential to add both in combination.

Claims (1)

[Scope of Claims] A block copolymer of styrene and butadiene having a styrene content of 60 to 90% by weight, (1) the following (A)
A styrenic resin shrink film containing at least one antioxidant selected from Group (2) and Group (B), (2) erucic acid amide, and (3) an inorganic filler and/or high impact polystyrene. (A) Group 2-t-butyl-6-(3'-t-butyl-5
'-Methyl-2'-hydroxybenzyl)-4-methylphenyl acrylate, 2,2'-methylene-bis-(4-methyl-6-t-butylphenyl), 2,6-di-t-butyl-4 -Methyl-phenol, octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenol)propionate (B) group 4,4'-thio-bis-(3-methyl 6-t-
butylphenol), 2-mercaptobenzimidazole, 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,
5,-triazine, triethylene glycol bis-3-
(3-t-butyl-4hydroxy-5methyl-phenyl)propionate, 2,2'-thiodiethylbis-[3
-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], distearyl-pentaerythritol-di-phosphite, 1,1,3-tris(2-
Methyl-4-di-tridecylphosphite-5-t-butylphenyl)butane, 4,4-butylidenebis(3-methyl-6-t-butylphenyl-di-tridecyl)phosphite, bis[2-methyl-4-( 3-n-tridecylthiopropionyloxy)-5-t-butylphenyl phosphite