JPH04115927A - Multilayer oriented film and its manufacture - Google Patents

Abstract

PURPOSE:To improve the suitability for successive biaxial orientation, pin hole- resistance, transparency, gas-barrier property, heat seal property and mechanical strength by using the layer composed of the blend of amorphous nylon with other nylon for the layer of polyamide resin. CONSTITUTION:The layer composed of the blend of amorphous nylon with other nylon is used for the layer A of polyamide resin. For instance, said layers are laminated in the order of A-B-C-D, A-C-B-C-D, B-A-C-D or B-C-A-C-D. Manufacture is achieved by the coextrusion in molten state from laminating dies by a plurality of extruders, and said extrudate is solidified under cooling most preferably. The orientation is achieved by the process of successive biaxial orientation by tenter method. The orientation temperature is 50-150 deg.C, and its draw ratio is in the range of 2-6 times, and these conditions are suitable for said process.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used as a film for food and other packaging such as shrink wrapping and pillow packaging, and has pinhole resistance, transparency, gas barrier property, heat roll property, and mechanical properties. The present invention relates to a multilayer stretched film with excellent physical strength and a method for producing the same.

[Conventional technology]

As a method of tightly packaging amorphous contents such as food and miscellaneous goods, shrink films made of polyvinyl chloride, polyethylene, polypropylene, etc. are used for packaging, and by applying heat to the film for a short period of time, the packaging material shrinks and the contents are removed. It has been used as a way to make things look better by making them fit better.

Depending on the content and distribution method, these films need to satisfy multiple functions such as mechanical strength and gas barrier properties, so the films are made into a laminated structure with several layers. It is conceivable to distribute various functions to each layer so that the layer has many functions overall.

For example, in the food industry, temperature during the distribution process,
Quality deterioration is likely to occur due to various changes in shape, color, taste, and aroma caused by moisture, oxygen, light, etc., as well as microorganisms such as bacteria and mold. Conventionally, the method of preserving foods without causing deterioration has been to add additives such as preservatives and antioxidants directly to foods. However, in recent years, regulations on additives to food have become stricter in the food processing industry, particularly in the meat processing and fish processing fields, and the amount of additives used has been reduced or stopped altogether. In order to ensure long-term shelf life and freshness, it has become necessary to develop a film that provides packaging materials with functionality such as oxygen gas barrier properties.

Furthermore, in the transportation stage of the food distribution process, conventional films have problems with mechanical strength, such as pinholes, depending on the transportation method.

On the other hand, in recent years, there has been a movement among food manufacturers to rationalize their production processes, both in terms of personnel and equipment, and in packaging machinery, bag-forming, filling-packing machines such as pillow-type packaging machines are often used for the purpose of speeding up and automating the process. It has become possible to do so.

Depending on such packaging machines, since the product flows at a high speed, the time required for heat roll is naturally shortened, which poses a problem of poor heat sealability. Therefore, good heat-sealability is an important characteristic required for packaging materials, but the disadvantage of polyethylene, which has traditionally been used as a sealing layer in multilayer films, is that the heat-sealability significantly decreases after stretching. It had

The present invention provides a polyamide resin layer as a mechanical strength imparting layer,
The gas barrier layer is made of ethylene.

Known methods for biaxially stretching a film include a sequential biaxial stretching method using a single tenter system and a simultaneous biaxial stretching method. Comparing these two methods, the sequential biaxial stretching method has a simpler device structure and is superior in productivity to the simultaneous biaxial stretching method.

However, aliphatic polyamide fats such as nylon 6 and nylon 6-6, which are conventionally used, are extremely difficult to stretch horizontally because they are oriented in the direction of intermolecular hydrogen bonding or horizontal stretching during longitudinal stretching in sequential biaxial stretching. It is.

As a method for solving these problems, a method of blending a polyamide containing a methaquinrylene group with an aliphatic polyamide is described in Japanese Patent Publication No. 51-29193 and the like. However, the film obtained by this method has insufficient transparency and does not meet the requirements as a packaging film.

Although an inflation method is also known as a simultaneous biaxial stretching method, it is not suitable for stretching a film having a complicated structure as in the present invention.

As a result of extensive research, the present inventors have found that by using a layer made of a blend of non-grade nylon and other nylon as the polyamide layer, successive biaxial stretchability is good, pinhole resistance is improved, and It was possible to obtain a multilayer stretched film with excellent transparency, gas barrier properties, heat sealability, mechanical strength, etc., and a method for producing the same. A multilayer stretched film containing non-grade nylon as a polyamide layer is described in JP-A-64-71749, but here the purpose of using non-grade nylon is to improve barrier properties. The stretching method is also carried out by the inflation method (tubular method), but the present invention aims to improve the successive biaxial stretching property using a tenter method, and to improve not only barrier properties but also pinhole resistance and transparency. The purpose of this invention is different from that of the above invention in that it is used for the purpose of simultaneously improving properties, mechanical strength, etc.

[Invention or problem to be solved]

An object of the present invention is to provide a multilayer stretched film that has excellent suitability for sequential biaxial stretching and also has excellent pinhole resistance, transparency, gas barrier properties, heat sealability, mechanical strength, etc., and a method for producing the same. It's about doing.

[Failure to solve the problem]

The present invention provides a multilayer stretched film comprising a polyamide resin layer (A), a saponified ethylene vinyl acetate copolymer resin layer (B), a modified polyolefin adhesive resin layer (C), and a heat seal resin layer CD. Resin (A)
is a multilayer stretched film characterized by using a layer made of a blend of non-grade nylon and other nylon, for example, from the outermost layer (A)-(B)-(C)-(D), ( A)-(C)-(B)-(C)-(D), (B)-(
8')-(C)-(D), or (B)-(C)
The present invention relates to a multilayer stretched film laminated in the order of -(A)-(C)-(D), and a method for producing the same.

The polyamide resin layer (A) used in the present invention is
This layer is made of non-grade nylon and other nylons and blends. Non-quality nylon can be obtained by pressurized melt condensation polymerization, decarboxylation condensation reaction, etc. using dicarboxylic acids, diamines, lactams, diisocyanates, etc. as raw materials. Examples of dicarboxylic acids include adipic acid, sheric acid, acelaic acid, terephthalic acid, and inophthalic acid. Diamines include hexamethylene diamine, trimethylhexamethylene diamine, isophorone diamine,
His-p-(aminonechlorohexyl)methane, His-p
-(aminonechlorohexyl)propane etc. are used.

Examples of the lactam include caprolactam and laurolactam.

As the diisocyanate, nphenylmethanesonanate, tolylene diisonanate, etc. are used.

Other nylons to be blended include nylon 6, nylon 12, nylon 11, and nylon 6, which are produced by the polycondensation reaction of ω-aminosulfonic acid, the polycondensation reaction of tribasic acid and dicarphonic acid amine, etc. -6, nylon 6-10, nylon 6-12, and copolymers or blends thereof.

Ethylene-vinyl acetate copolymer saponified resin (hereinafter referred to as E
It is abbreviated as VOH. ) Layer (B) has a softening temperature (flow tester method) of 150°C to 175°C, an ethylene content of 25 to 75 mol%, and a saponification degree of vinyl acetate in the copolymer of 90% or more. Good.

Anhydrides of monobasic unsaturated fatty acids such as acrylic acid and methacrylic acid, or dibasic unsaturated fatty acids such as maleic acid, fumaric acid, and itaconic acid, that is, maleic anhydride, etc., are added to Ropyrene Elasto by chemical treatment. An acid-modified olefin resin obtained by bonding with is used.

The heat seal resin layer (D) is made of low density polyethylene (hereinafter abbreviated as LDPE), Lanier low density polyethylene (LLDPE), medium density polyethylene (MDPE).
, high density polyethylene (HDPE), polypropylene (
PP), etc., and ethylene-vinyl acetate copolymer (EVA), which is an ethylene copolymer.
, ethylene methyl methacrylate copolymer, (EM
MA), ethylene-ethyl acrylate copolymer (EE
A), ethylene-methyl acrylate copolymer (EMA
), chelene-ethyl acrylate maleic anhydride copolymer (E-EA-MAR), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ionomer (1ON), etc. Can be used with resin.

The total thickness of the multilayer stretched film of the present invention is 10 to 150 μm
A plastic film having a thickness within this range is suitable as a packaging film for use in food packaging and the like.

The multilayer stretched film of the present invention has (A)-(B) from the outermost layer.
-(C)-(D), (A)-(C)-(B)-(C)-(D), (B)-(
A)-(C)-(D), or (B)-(C)-(A
) - (C) - (D) Adjacent stacked structure is taken in the order. Note that the outermost layer, the polyamide resin layer (A), the saponified ethylene-vinyl acetate copolymer resin layer (B), and the innermost layer, the heat seal resin layer (D), have mechanical suitability with the packaging machine. An appropriate amount of a suitable lubricant may be added to improve the performance.

The most suitable method for producing the multilayer film of the present invention is a coextrusion method using a plurality of extruders, in which melt extrusion is performed from a laminated die, followed by cooling and solidification. The stretching method is a sequential biaxial stretching method using a tenter, and the stretching temperature is 50 DEG C. to 150 DEG C., and the stretching ratio is suitably within the range of 2 to 6 times. After stretching, a non-heat-shrinkable multilayer biaxially stretched film can be obtained by heat-setting at a stretching temperature within the range of -5°C to 180'C.

[Examples 1 to 3] Table 1 shows examples and comparative examples of the present invention. All films were melt-extruded from a multilayer coextrusion die by T-die extrusion to produce films with a thickness of 450 μm.

The film has a polyamide resin layer, adhesive resin layer (1)/EVOH/adhesive resin layer (2)/Hitonol resin, and the thickness ratio of each layer is 15/10/10.
/1015504.

The polyamide resin layer is made of non-grade nylon (hereinafter referred to as A-Ny
It is abbreviated as ) Made by Mitsui DuPont Polychemical ■
As a comparative example, A-N
y and 6-Ny alone were also used.

Other raw materials for the resins constituting each layer include the adhesive resin layer (
1): Atmer NF -500VOH manufactured by Ii Petrochemical ■ Ehar F Adhesive resin layer (2) Mersen P 2030W heat seal resin manufactured by Tosoh ■ Himilan 16013 manufactured by Mitsui DuPont Polychemical ■ was used. The obtained multilayer film was sequentially biaxially stretched using a new biaxial stretching experiment device manufactured by Toyo Seiki. The stretching temperature was 80°C, and the stretching ratio was 3 times in both the length and width. Table 1 shows the successive biaxial stretching suitability of each sample.

As shown in Comparative Examples 1 and 2 in Table 1, when 8-Ny was used alone and when A-NY was used at a ratio of 80%, the film broke during stretching due to the large load during stretching, and the stretching conditions No good film was obtained even after shaking. Also 6-N
Even when y was used alone, stretching unevenness occurred during transverse stretching, and a good film could not be obtained. On the other hand, the films of Examples 1 to 3 according to the present invention could be stretched without any particular problems, and good films were obtained.

[Example 4] A film of EVOH/polyamide resin layer/adhesive resin layer/EEA was melt-extruded from a multilayer coextrusion die in the same manner as in Example 1 to produce a 350 μm thick film. The thickness ratio of each layer is +5/20/1
It was set to 0/55%.

The polyamide resin layer is A-Ny/6-Ny (blend ratio = 50% 150%, raw materials are the same as in Example 1),
As a comparative example, nylon MXD6 (manufactured by Mitsubishi Gas Chemical
MX nylon 6580) and 6-Ny (manufactured by Ube Industries) 1
030B) (blend ratio = 70%/3
0%), and 6/66 copolymer nylon (manufactured by Ube Industries)
5033B) was used.

Other raw materials are: VOH Kuraray Eval E 105AD Adhesive resin layer Mitsui Petrochemical Atmer V F-500EEA
Evaflex A made by DuPont Mitsui Polychemicals
-701 was used.

The obtained multilayer film was sequentially biaxially stretched using a biaxial stretching experimental apparatus. The stretching temperature was 75°C.
The stretching ratio was 2.5 times in both length and width. The light transmittance and haze of the obtained multilayer biaxially stretched film are expressed as A
It was measured by the STMD-1003 method and the results shown in Table 2 were obtained.

Table 2 It was measured.

As shown in Table 3, the oxygen permeability after stretching was significantly improved.

〔Effect of the invention〕

The multilayer stretched film according to the present invention has excellent successive biaxial stretching suitability, pinhole resistance, transparency, and gas barrier properties.
It also has very good physical properties such as hardness, heat rollability, and mechanical strength, making it suitable as a packaging film for foods and other items.

The film of the present invention has very good transparency compared to the film of the comparative example.

Claims (3)

[Claims] (1) In a multilayer stretched film including a polyamide resin layer (A), a saponified ethylene-vinyl acetate copolymer resin layer (B), a modified polyolefin adhesive resin layer (C), and a heat seal resin layer (D), Polyamide resin layer (A)
A multilayer stretched film characterized by using a layer made of a blend of amorphous nylon and other nylon. (2) The multilayer stretched film is formed from the outermost layer to (A)-(B)-(C)-(D), (A)-(C)-(B)-(C)-(D), (B) −(
Claim (1) describes a layered structure in the order of A)-(C)-(D) or (B)-(C)-(A)-(C)-(D). multilayer stretched film. (3) The multilayer stretched film according to claim (1) or (2), wherein the multilayer stretched film is sequentially biaxially stretched at a stretching temperature of 50 to 150°C and a stretching ratio of 2 to 6 times. Production method.