JP2557369B2 - Polyethylene resin composition for stretchable film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a polyethylene resin composition for stretchable films. More specifically, the present invention relates to a stretchable film polyethylene resin composition excellent in stretchability using a copolymer of ethylene and an α-olefin having 3 or more carbon atoms.

[Conventional technology]

Conventionally, casting using a sand mold has been made tough by tamping the mold (sand mold), and the mold shape is maintained by the rigidity of the mold itself. In recent years, a method has been proposed in which casting is performed by keeping the shape of the mold by covering the surface of the mold with a synthetic resin film and maintaining the shape of the mold.

That is, in FIG. 1 to FIG. 5, the thermoplastic resin film 3 is vacuum-adhered to the molding surface 2 of the original mold 1 while heating it, and the film 3 is vacuum-formed into the same shape as the master mold shape 1, Next, the frame body 4 is contacted from both sides of the film 3 on the molding surface, the frame body 4 is filled with a particulate matter, for example, sand, and the air inside the frame body 4 is deaerated to obtain a negative pressure (reduced pressure). By doing so, the film is pulled toward the frame body 4 side, and even after the frame body 4 is removed from the circular mother die 1, a mold in which the shape of the film is maintained in the molded shape of the original mother die 1 is obtained. The casting method of this mold is abbreviated as V-process hereinafter.

Most of the thermoplastic resin films used for the V-process are those made of ethylene-vinyl acetate copolymer.

[Problems to be solved by the invention]

In the above-mentioned V-process, the thermoplastic resin film is heated to be softened so that it can be vacuum-adhered to the original mold. Therefore, heating equipment is required, and it is necessary to increase the thickness of the film in order to maintain the strength when the film is softened by heating, which is not always economical in terms of film cost and equipment. Can't be said to be advantageous.

[Means for solving problems]

In view of the above situation, the inventors of the present invention have made extensive studies to produce a highly stretchable film that can be vacuum-adhered without heating as a film used in the V-process, and as a result, ethylene having specific physical properties Α- with 3 or more carbon atoms
When a film is formed using a resin composition prepared by mixing a specific amount of an aromatic carboxylic acid ester plasticizer in a copolymer with an olefin, the obtained film has high stretchability and is sufficient even if it exceeds the elastic limit. It has excellent mechanical strength,
When used in a process, they have found that they can be vacuum-adhered to a master mold without heat treatment, and completed the present invention.

That is, the gist of the present invention is that the melt index is 2 g.
/ 10 minutes or less and a density of 0.91 g / cm ³ or less 100 parts by weight of a copolymer of ethylene and an α-olefin having 3 or more carbon atoms and 0.1 to 20 parts by weight of an aromatic carboxylic acid ester plasticizer It exists in a polyethylene resin composition for stretchable film formed by blending.

 Hereinafter, the present invention will be described in more detail.

The present invention is a stretchable film polyethylene resin composition comprising a copolymer of ethylene having specific physical properties and α-olefin having a carbon number of 3 or more and a specific amount of an aromatic carboxylic acid ester plasticizer. .

The copolymer of ethylene and an α-olefin having 3 or more carbon atoms (hereinafter simply referred to as an ethylene copolymer) used in the present invention has a melt index of 2 g / 1.
0 minutes or less, preferably 0.1-2 g / 10 min range, and more preferably in the range of 0.2~1g / 10 min, and a density of 0.91 g / cm ³
The following, preferably 0.85-0.91 g / cm ³ , more preferably
It is in the range of 0.85 to 0.90 g / cm ³ , and the flow ratio is 30 or less, preferably 5 to 25, more preferably 10 to 25. If the melt index is higher than the upper limit, the film becomes too brittle, and if the density is higher than the upper limit, it lacks in softness, the stretchability of the film becomes insufficient, and the physical properties of the film deteriorate when the flow ratio is higher than 30. It is not preferable. The ethylene copolymer preferably has an elongation of 1000% or more, and preferably 1200% or more.

In the method of the present invention, the melt index is JIS K6.
It is the value measured at 190 ° C according to 760, and elongation is JIS K6.
It is a value measured according to the measuring method of elongation at break in the section of tensile test of 301, the density is a value measured according to JIS K6760, and the flow ratio is the melt index measuring device. Using a shear force of 10 ⁵ dynes / cm ² (load 1113 g)
It is the ratio of the extrusion rate (g / 10 minutes) of 10 ⁶ dyne / cm ² (load 11131 g).

Examples of the α-olefin copolymerized with ethylene include propylene, butene-1, pentene-1, hexene-1,
4-methylpentene-1 and the like. Of these, propylene and butene-1 are preferable.

The ethylene copolymer in the present invention also includes a terpolymer obtained by copolymerizing ethylene, an α-olefin having 3 or more carbon atoms, and a non-conjugated diene. Examples of such non-conjugated dienes include 1,4 hexadiene, dicyclopentadiene and ethylidene norbornene.

The ethylene copolymer is a Ziegler-Natta-based catalyst, especially ethylene and α-olefin using a catalyst composed of a power compound such as vanadium oxytrichloride and vanadium tetrachloride and an organoaluminum compound, and optionally a non-conjugated diene. It can be produced by copolymerizing and.

The ethylene content of the ethylene copolymer used in the present invention is preferably in the range of 40 to 90 mol%, and the α-olefin content is preferably in the range of 10 to 60 mol%. .

The resin composition of the present invention comprises the above ethylene copolymer and a specific amount of an aromatic carboxylic acid ester plasticizer.

As the aromatic carboxylic acid ester-based plasticizer, various compounds such as esters of benzoic acid, phthalic acid and trimellitic acid, which are commonly used as plasticizers for vinyl chloride resins, can be used. Examples of the benzoic acid ester plasticizer include diethylene glycol dibenzoate and the like. Examples of the phthalate ester plasticizer include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, diheptyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate, di-isooctyl phthalate, dinonyl phthalate, diisononyl phthalate, Didecyl phthalate, diisodecyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, diphenyl phthalate, dibenzyl phthalate, di (mixed alcohol) phthalate, dibutoxyethyl phthalate, butyl lauryl phthalate, butyl benzyl phthalate, butyl octyl phthalate, octyl decyl phthalate, butyl. Examples thereof include cyclohexyl phthalate.

Examples of the trimellitic acid ester plasticizer include, for example,
Tri-2-ethylhexyl trimellitate, tri-n-
Octyl trimellitate, tridecyl trimellitate,
Examples include tributyl trimellitate, dibutyl benzyl trimellitate, and the like.

These aromatic carboxylic acid ester plasticizers can be used alone or in admixture of two or more.

The stretchable film polyethylene resin composition of the present invention comprises 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, and more preferably 0.2 to 5 parts by weight of the plasticizer per 100 parts by weight of the above-mentioned ethylene copolymer. It is a range. When the amount of the plasticizer is less than the lower limit, the film formability is remarkably deteriorated and the film is roughened and blocking occurs, which is not preferable. On the other hand, if the amount is more than the upper limit, the kneading with the ethylene copolymer will be significantly deteriorated and the film strength will be significantly lowered, which is not preferable.

The stretched raw film polyethylene resin composition of the present invention is obtained by dry blending the above-mentioned components in a blender or the like as they are or by dry blending with an extruder or the like, and then using a compound that has been pelletized by a usual film forming method. It can be formed into a film.

As the film forming method, an ordinary film forming method can be applied. In particular, in the T die film forming method, when the extrusion temperature is 150 to 250 ° C., and the die is formed with a lip gap of 0.5 to 4.0 mm under a draft ratio of 10 to 40, A particularly preferable film can be obtained. The draft rate is a value calculated by the following formula.

Further, the polyethylene resin composition for stretched raw film of the present invention may be blended with an anti-blocking agent, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a pigment, a stabilizer and the like depending on the purpose of use. .

[Action]

In the method of the present invention, when a film is prepared by using a resin composition in which a specific amount of an aromatic carboxylic acid ester plasticizer is blended with a copolymer of ethylene having physical properties and an α-olefin having 3 or more carbon atoms. , With high extensibility,
Moreover, sufficient mechanical strength can be imparted even if the elastic limit is exceeded.

Example 1 Ethylene-propylene copolymer (melt index (MI): 0.4 g / 10 minutes, density: 0.86 g / cm ³ , elongation: 1300%, flow ratio: 17, propylene copolymerization amount: 22% by weight) 100 2.5 parts by weight of dioctyl phthalate (abbreviated as DOP) was added to parts by weight, and after blending with a Henschel mixer, the mixture was melt-kneaded at a temperature of 250 ° C. with an extruder having a cylinder diameter of 50 mm and extruded into pellets. This is extruded using a T-die molding machine equipped with a 40 mmφ extruder manufactured by Sumitomo Heavy Industries, Ltd. with a lip clearance of 0.7 mm, a die length of 480 mm, and a cooling air knife (110 mm from the die lip, room temperature). Temperature 18
0 ℃, extrusion rate 15kg / hr, winding speed 2.0m / min, draft rate 28
The film was extruded into a film under the conditions of, and cooled at a cooling roll temperature of 20 ° C. to form a film having a thickness of 25 μm.

Table 1 shows the results of measuring various physical properties of the obtained film. The physical properties in Table 1 were measured by the following measuring methods.

(A) Surface condition of the film It is visually determined whether or not so-called shark skin has occurred.

(B) Film friction coefficient (COF) 160 x 80 mm and 1 with the film extrusion direction as the longitudinal direction
Cut out two test pieces of 60 x 63.5 mm.

A 160 x 80 mm film is fixed to a tiltable plate with felt attached to the surface.

(Longitudinal direction is the direction of inclination.) 160 × 63.5 mm film is fixed so that the lower surface is a rectangle of 100 × 60 mm (sponge is attached) and covers the lower surface of a 1 kg weight.

The weight is placed on the film that has been slid onto the slant plate, and the slant plate is gradually inclined to allow the weight to start sliding (tan θ).
Measure

 The same operation is repeated three times and the average value is used.

(C) Adhesiveness Prepare a mold with a hole with a diameter of 10 mm and a depth of 7 mm, and fix it on the upper part of this mold with the film to be tested in close contact with the film. To the inside of the hole.

The case where the film was in contact with the bottom surface of the hole by 40 mm ² or more and there was no tear or the like was defined as good, and the case where the contact area was 40 mm ² or less or the film was torn was defined as defective.

(D) Tensile elongation Measured according to JIS Z-1702.

Examples 2 to 4 and Comparative Examples 1 to 4 Examples were carried out except that ethylene-propylene copolymers having the physical properties shown in Table 1 were used, and the type and blending ratio of the plasticizer were changed as shown in Table 1. The procedure was as in Example 1. Table 1 shows the results.

Comparative Example 5 The procedure of Example 1 was repeated except that the ethylene-propylene copolymer was changed to an ethylene-vinyl acetate copolymer (vinyl acetate content 36%) and the conditions of Table 1 were used. Table 1 shows the results.

Comparative Example 6 Example 1 was repeated except that 2.5 parts by weight of dioctyl phthalate was replaced by 1.5 parts by weight of monoglycerin oleate and 1.0 part by weight of sorbitan oleate in Example 1.
I went the same way. Table 1 shows the results.

Comparative Example 7 Example 1 was repeated except that 2.5 parts by weight of dioctyl phthalate was replaced with 1.5 parts by weight of monoglycerin oleate and 1.0 part by weight of polyethylene glycol sorbitan oleate in Example 1. Table 1 shows the results.

Comparative Example 8 The procedure of Example 1 was repeated, except that 2.5 parts by weight of dioctyl phthalate was replaced by 1.5 parts by weight of diglycerin oleate and 1.0 part by weight of sorbitan laurate. Table 1 shows the results.

[Effects of the Invention] The film obtained from the polyethylene resin composition for stretchable film of the present invention has high stretchability, and has moldability and mechanical strength even if the elastic limit of the film is exceeded. When it is used in the V process, it can be vacuum-adhered to the original mold without heat treatment.

Further, the above-mentioned film can be used in applications where it is desirable to use an extensible film, for example, packaging materials such as stretch wrapping, and simple finger bags and gloves that can be formed by finger-stretching.

[Brief description of drawings]

1 to 5 are partially cutaway front views for explaining the V-process in the order of steps. In the figure, 1 is a mother die, 2 is a molding surface, 3 is a film, and 4 is a frame.

Claims (1)

(57) [Claims] 1. An aromatic carboxylic acid is added to 100 parts by weight of a copolymer of ethylene having a melt index of 2 g / 10 minutes or less and a density of 0.91 g / cm ³ or less and α-olefin having 3 or more carbon atoms. Polyethylene resin composition for stretchable film containing 0.1 to 20 parts by weight of ester plasticizer