JPS61221258A - Resin composition - Google Patents

Abstract

PURPOSE:To obtain a resin compsn. giving a heat-shrinkable film which can be oriented at a relatively low temp. and has excellent heat shrinkability, containing a block copolymer and a petroleum resin or a cumarone resin or a hydrogenated product thereof. CONSTITUTION:A resin compsn. contains 99-40wt% block copolymer composed of a styrene hydrocarbon and a conjugated diene hydrocarbon, 0-40wt% polystyrene and 1-40wt% petroleum resin having a softening point of 60 deg.C or above or cumarone resin or hydrogenated product thereof. The ratio of the styrene hydrocarbon to the conjjugated diene hydrocarbon in the block copolymer is such that the styrene hydrocarbon is 50-90wt% and the conjugated diene hydrocarbon is 50-10wt% said compsn. is extruded through a T-die or a ring die at 160-240 deg.C into a flat or tubular molding, which is when oriented mono-, bi- or polyaxially, thus molding into the desired heat-shrinkable film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a resin composition that provides a heat-shrinkable film by -axial stretching or biaxial stretching.

[Conventional technology]

Conventionally, heat-shrinkable films made from polyvinyl chloride resin have been widely used, but these polyvinyl chloride resin films have problems such as hydrogen chloride being generated when incinerated. A replacement product was needed.

Therefore, as a solution to these problems, for example,
A film obtained by two-wheel stretching a resin composition in which a styrene resin is blended with a block copolymer of a styrene hydrocarbon and a diene hydrocarbon (Japanese Unexamined Patent Publication No. 1983-108.177), Improved heat shrinkability at low temperatures (JP-A-57-25.349 and JP-A-58-1
51.219) etc., styrenic films mainly composed of block copolymers made of styrene hydrocarbons and conjugated diene hydrocarbons have been proposed.

[Problem that the invention seeks to solve]

However, the former film has a heat shrinkage temperature of 10
If it is not higher than 0°C, it does not show sufficient heat shrinkability and there is a problem with shrinkage at low temperatures.The latter film, which solved this problem, has restrictions on the structure, molecular weight, molecular weight distribution, etc. of the block copolymer. However, there was a problem in that the materials that could be used were limited.

(Means for Solving the Problems) The present invention has been devised in view of these points of view, and therefore does not generate hydrogen chloride or cause hygiene problems, and can be stretched at relatively low temperatures and is heat-shrinkable. The present invention provides a resin composition that provides a heat-shrinkable film with excellent properties.

That is, the present invention uses 99 to 40% by weight of a block copolymer consisting of a styrene hydrocarbon and a conjugated diene hydrocarbon.
This is a resin composition for a heat-shrinkable film containing 120 to 40% polyester, and 1 to 40% by weight of a petroleum resin or coumaron resin having a softening point of 60° C. or higher, or a hydride thereof.

In the present invention, the styrenic hydrocarbons constituting the block copolymer include styrene, 0-methylstyrene,
Examples of the conjugated diene hydrocarbon include p~methylstyrene and 1,3-dimethylstyrene, and examples of the conjugated diene hydrocarbon include butadiene, isoprene, and 1,3-pentadiene. These styrenic hydrocarbons or conjugated diene hydrocarbons may be used alone or in a mixture of two or more.

The ratio of styrenic hydrocarbons and conjugated diene hydrocarbons constituting the block copolymer is not particularly limited, but preferably 50 to 90% by weight of styrene hydrocarbons and 50 to 90% by weight of conjugated diene hydrocarbons. 10% by weight, more preferably 60-80% by weight of styrenic hydrocarbons
and 40 to 20% by weight of conjugated diene hydrocarbon.

In addition, the structure of the block copolymer used in the present invention is expressed by the following general formula (% formula %) [However, A represents a styrene hydrocarbon polymer block, and B represents a conjugated diene hydrocarbon polymer block. and n represents a positive integer. [However, A and B are the same as above, n is an integer of 3 or more, and Y is a radial polymer. It is the residue of the polyfunctional coupling agent used in the conjugation format. ] may be used, but the latter star block copolymer is preferred. The structural form of the block may be a complete block structure or a so-called tapered block structure in which AB cram copolymer is present at the transition portion between block A and block B.

The polystyrene used in the present invention may be general so-called GP polystyrene, and its addition m is usually 0 to 4.
0% by weight, preferably 1-30% by weight, more preferably 2-20% by weight. This polystyrene is added for the purpose of improving the stiffness, transparency, and/or gloss of the film, but the addition interval of polystyrene is 40
If it exceeds % by weight, the stretching temperature will increase, and impact strength will decrease and cracks will easily occur. In addition, as this polystyrene, one with a low molecular weight, such as a weight average molecular weight ffi
When a material having a (M W ) of 50,000 or less is used, stretching can be performed at a lower temperature and the heat shrinkage properties are also improved.

In addition, as the petroleum resin used in the present invention, C5 or C5
Examples include aliphatic petroleum resins containing 5 to C9 fractions as main components, dicyclopentadiene petroleum resins, and C9 petroleum resins containing aromatic hydrocarbons as main components. Examples of the coumaron resin include coumaron resin, coumaron-indene resin, coumaron-indene-styrene copolymer, and indene resin. Examples of these hydrides include those obtained by completely or partially hydrogenating the above-mentioned various petroleum resins and various coumaron resins. Preferably, it is nearly completely hydrogenated.

Among these resins, for example, Cumaron resin is made from the 160-180°C fraction of coal tar and heavy light oil from coke oven gas, and after washing with sulfuric acid and water, it is treated with boron trifluoride. It can be produced by polymerizing using a complex salt, aluminum chloride, etc. as a catalyst, and then removing the catalyst and solvent components.

The softening point of the petroleum resin or coumaron resin or hydride thereof (JIS 2207 ring and ball method) is 60°C.
It is important that it is above, preferably 60 to 120
℃, more preferably 70 to 100℃. The lower the softening point, the better the stretchability and heat shrinkability at low temperatures will be exhibited, but if the softening point is lower than 60°C, workability during mixing and storage stability in summer, etc. will deteriorate.

In addition, the amount of these petroleum resins or coumaron resins or their hydrides added is usually 1 to 30% by weight.
, preferably 5 to 20% by weight. If the amount added is less than 1% by weight, the stretching effect at low temperatures will be insufficient and the heat shrinkability will not be improved much. On the other hand, if the amount added exceeds 30% by weight, cracks are likely to occur during sheet molding and workability will also decrease. Incidentally, when the amount of petroleum resin or coumaron resin added increases, the film becomes colored due to these resins, but this problem can be solved by using a hydride obtained by hydrogenating these resins.

The resin composition of the present invention containing the above-mentioned block copolymer, polystyrene, and petroleum resin or coumaron resin or hydride thereof can be prepared by a tri-blend method using a conventional Henschel mixer, a ribbon blender, a blender, etc. The melt mixing method using a general mixer such as an open roll, co-kneader, or extruder, or the method of dissolving or dispersing each component in a solvent, mixing them, and then removing the solvent by heating, etc., as appropriate. Prepare by uniformly mixing and kneading according to the method described in . This resin composition may be prepared at the time of molding the product, or may be molded in advance into a belen shape.

The resin composition thus obtained is heated at 160 to 240°C, preferably at 18°C, from a normal T-die or annular die.
A heat-shrinkable film can be formed by uniaxially, biaxially or multiaxially stretching a molded product extruded into a flat or tubular shape at 0 to 220°C.

The stretching method at this time may be any of the commonly used tenter method or tubular method.
There is no particular restriction on the stretching direction,
- In the case of axial stretching, either the extrusion direction or a direction perpendicular to this extrusion direction may be used, and in the case of two-wheel stretching, the longitudinal direction and the transverse direction can be carried out simultaneously or separately. Roughly speaking, the stretching ratio is 1.5 to 8 times in both directions.
It is preferable to stretch the film 2 to 6 times, and the thickness of the stretched film is preferably about 20 to 80 μm.

In preparing the resin composition of the present invention, various additives conventionally used in this type of resin composition, such as ultraviolet absorbers, antioxidants, stabilizers, colorants, and fillers, may be added. , a lubricant, etc. can be added.

〔Example〕

Hereinafter, the resin composition of the present invention will be explained based on Examples and Comparative Examples.

Example 1 Star-shaped block copolymer consisting of 75% by weight of styrenic hydrocarbon and 25% by weight of conjugated diene hydrocarbon (product name: Niiniichi Jin KR-05, manufactured by Phillips Vetroleum 1)
90 weight 8 parts and 10 weight parts of Kumaron resin (Nippon Steel Chemical Co., Ltd. trade name: Nippon Steel Kumaron G-90, softening point: 96°C) were melt-mixed in an extruder and kneaded uniformly to form a resin composition. I got something.

Example 2 The use B of the block copolymer used in Example 1 was 89 parts by weight, and polystyrene (trade name: Estyrene G-32 manufactured by Nippon Steel Chemical) llfffi part and Coumaron resin (trade name manufactured by Nippon Steel Chemical) were added. A resin composition was obtained in the same manner as in Example 1 using (trade name: KUMARON V-120, softening point = 118°C) and 10 overlapping parts.

Example 3 85 parts by weight of the same block copolymer as in Example 1, 5 parts by weight of polystyrene the same as in Example 2, petroleum resin (Toho Petroleum Resin @ J product name: Hi-Resin 5, softening point near 1°C>
A resin composition was obtained in the same manner as in Example 1 using a 10-fold assembly.

Example 4 Same as Example 1, using 40 parts by weight of the same block copolymer as in Example 1, 30 parts by weight of the same polystyrene as in Example 2, and 30 parts by weight of the same coumaron resin as in Example 2. Example 5 60 parts by weight of the same block copolymer as in Example 1, 20 parts by weight of polystyrene as in Example 2, and 20 parts by weight of Coumaron resin as in Example 1 were used. A resin composition was obtained in the same manner as in Example 1.

Example 6 85 parts by weight of the same block copolymer as in Example 1 and low molecular weight polystyrene (trade name: Hymer-5T- manufactured by Sanyo Kasei Co., Ltd.
95) A resin composition was obtained in the same manner as in Example 1 using 10 parts by weight and 5 parts by weight of the same petroleum resin as in Example 2.

Example 7 50 parts by weight of the same block copolymer as in Example 1 and 50 parts by weight of styrenic hydrocarbon! [10!1 parts by weight of a block copolymer consisting of 11% and 50% by weight of conjugated diene hydrocarbon (product name: Cariflex TR4122 manufactured by Shell Chemical ■), 30 parts by weight of the same polystyrene as in Example 2, and Example A resin composition was prepared in the same manner as in Example 1, using 10 parts by weight of the same petroleum resin as in Example 2.

Example 8 85 parts by weight of the same block copolymer as in Example 1, 10 parts by weight of the same low molecular weight polystyrene as in Example 6, and a hydride of petroleum resin (manufactured by Arayo Kagaku ■, trade name: Alcon P70, softening point near A resin composition was obtained in the same manner as in Example 1 using a 5-fold interlayer (0°C).

Comparative Example 1 A resin composition was obtained in the same manner as in Example 1 except that only the same block copolymer as in Example 1 was used.

Comparative Example 2 99 parts by weight of the same block copolymer as Example 1 and Example 2
A resin composition was obtained in the same manner as in Example 1 using 1 part by weight of the same polystyrene.

Biaxially stretched.

Comparative Example 3 70 parts by weight of the same block copolymer as Example 1 and Example 2
A resin composition was obtained in the same manner as in Example 1 using 30 parts by weight of the same polystyrene.

Comparative Example 4 Using the same block copolymer 90 weight 8a as in Example 1 and 10 parts by weight of the same low molecular weight polystyrene as Example 5,
A resin composition was obtained in the same manner as in Example 1.

Comparative Example 5 50 parts by weight of the same block copolymer as in Example 1, 20 parts by weight of the same other block copolymer as used in Example 7, and 30 parts by weight of polystyrene the same as in Example 1 were used. ,
A resin composition was obtained in the same manner as in Example 1.

The resin compositions obtained in each of the above Examples and Comparative Examples were extruded at 210°C using a 40 mm diameter extrusion machine equipped with a T-die with an effective lip width of 300 m to form a sheet with a thickness of about 0.25 m, Scattered light transmittance (Rs
t) and total light transmittance (Rt), R8t/Rt
The cloudiness (haze) determined from the formula X100 was measured. The results are shown in Table 1.

Next, the above-mentioned sheet was subjected to two-wheel stretching in each of the longitudinal and lateral directions at a stretching ratio of 2 times while changing the temperature using a simultaneous biaxial stretching machine, and the lowest temperature at which the stretching was possible was determined. The results are shown in Table 1.

Furthermore, as a result of examining the heat shrinkage rate of the films obtained using the resin compositions of each of the above examples at a temperature 15°C or more lower than the lowest temperature at which stretching is possible, all showed a heat shrinkage rate of 20% or more. Indicated.

Table 1 [Effects of the Invention] The resin composition of the present invention can be stretched at a relatively low temperature compared to a styrene film mainly composed of a block copolymer composed of a styrene hydrocarbon and a conjugated diene hydrocarbon. This also provides a heat-shrinkable film with excellent heat-shrinkability.

Patent applicant Nippon Steel Chemical Co., Ltd. Representative Patent attorney Katsuo Naruse (2 others)

Claims (1)

[Claims] (1) 99 to 40% by weight of a block copolymer consisting of a styrene hydrocarbon and a conjugated diene hydrocarbon, 0 to 40% by weight of polystyrene, and a petroleum resin or coumaron resin with a softening point of 60°C or higher, or a hydride thereof. 1-40% by weight
A resin composition for a heat-shrinkable film, comprising: