JPH0892400A - Surface treatment for thermoplastic resin sheet - Google Patents

Abstract

PURPOSE: To provide a molded resin product having the gas barrier properties which do not lower, even when heat and/or force are applied thereto on fabrication or on use. CONSTITUTION: A olefinic resin is melt-extruded and the undrawn film is oriented in the longitudinal direction, heated at 60-100 deg.C and subjected to corona discharge treatment of 30-10w.min./m<2> . Then, this longitudinally oriented film is coated, on the corona discharged surface, with a solution of an ethylene-vinyl alcohol copolymer in which the content of the ethylene component is 20-45 mole%, dried and then oriented in the traverse direction, further treated with the corona discharge of 30-100w.min./m<2> on the coated surface. Then, evaporation-deposited layer of inorganic oxide is formed on the oriented surface of the ethylene-vinyl alcohol copolymer after corona discharge treatment to give a molded resin product having a inorganic oxide layer on the copolymer layer and gas barrier properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin molded product for packaging which is used for protecting foods, electronic parts and the like and has an excellent gas barrier property.

[0002]

2. Description of the Related Art It has been proposed to wrap foods, electronic industrial parts and the like in a film or a container to suppress oxygen permeation to prevent oxidation of the contents and maintain quality for a long time. For example, Japanese Patent Publication No. 53-12953, JP-A-4-3535.
No. 32 discloses a general formula SixOy (x = 1, 2, on at least one surface of a flexible plastic film such as polyethylene terephthalate, cellophane, nylon, polypropylene, or polyethylene having a thickness of 5 to 300 μm.
thickness of silicon oxide having a composition of y = 0, 1, 2, 3) 10
Disclosed is a transparent flexible plastic film having a high degree of air permeation resistance and moisture permeation resistance, which is provided with a transparent vitreous thin film layer of 0 to 3000 angstrom.

Further, in Japanese Patent Laid-Open No. 63-23794, a metal oxide of one kind of metal selected from the group consisting of In, Sn, Zn, Zr and Ti on at least one surface of the flexible plastic film. There is disclosed a transparent gas-barrier resin film in which a transparent heat-sealable resin film is coated thereon by sputtering. When the film material is a resin having a polar group such as polyethylene terephthalate, nylon, and cellophane, the film and the inorganic oxide film have sufficient adhesion and good gas barrier properties.

However, even if a vapor-deposited film made of the above-mentioned inorganic oxide is formed on the surface of a molded product of a polyolefin having no polar group such as polypropylene or polyethylene, it has a stable gas barrier property that can withstand practical use. I can't get it. That is, since the adhesion between the polyolefin molded product and the thin film is weak, when laminating a heat-sealable resin having a melting point lower than the melting point of the polyolefin constituting the molded product in order to impart heat-sealing property to this vapor deposit, , When this laminate is used for secondary processing such as bag making or lid sealing, or when these bags are used, or when the contents are filled in a container and further sterilized by retort, external stress or heat is applied to the molded product. In addition, the inorganic oxide thin film is peeled off from the polyolefin molded product, the gas barrier property is deteriorated, and there is a problem that it cannot be put to practical use.

[0005]

DISCLOSURE OF THE INVENTION The present invention is an olefin resin molded article having an inorganic oxide thin film deposited thereon, which is excellent in gas barrier properties, and the inorganic oxide thin film does not peel off during secondary processing or use of the product. It is an object of the present invention to provide a resin molded product that does not deteriorate in gas barrier property.

[0006]

According to the present invention, an unstretched film obtained by melt-extruding an olefin resin is stretched in the machine direction and then heated to 60 to 100 ° C. for 30 to 100 w.
Min / m ² corona discharge treatment is performed, and then the corona-treated surface of the longitudinally stretched film is coated with an ethylene-vinyl alcohol copolymer coating solution having an ethylene content of 20 to 45 mol%, dried and then in a tenter. Stretching in the transverse direction and further subjecting this coating surface to a corona discharge treatment of 30 to 100 w · min / m ² for vapor deposition of an inorganic oxide on the stretched film surface of the ethylene-vinyl alcohol copolymer of the laminated film obtained. It is intended to provide a resin molded article having a gas barrier property having a film-formed structure.

[0007]

[Function] By combining an ethylene-vinyl alcohol copolymer and an inorganic oxide, a good gas barrier property can be obtained, and further, the alcoholicity of a corona discharge treated product of a thin stretched film of the ethylene-vinyl alcohol copolymer is obtained. Due to the presence of the hydroxyl group and the carboxyl group, the adhesion between the substrate and the inorganic oxide vapor deposition film becomes stronger.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The olefin resin for the base material layer is propylene homopolymer, propylene / ethylene copolymer, propylene / butene-1 copolymer, propylene / 4.
-Propylene-based resin such as methylpentene-1 copolymer,
Ethylene resins such as branched low-density polyethylene and linear polyethylene, or olefin resins modified with α, β-unsaturated carboxylic acid can be used. These may be used as a mixture of two or more kinds, or may be used by being laminated. Further, it may contain 0.01 to 2% by weight of an anti-blocking agent, a nucleating agent, a stabilizer, a lubricant and the like.

Coating of ethylene / vinyl alcohol copolymer
The ethylene / vinyl alcohol copolymer for liquid coating liquid is a copolymer of ethylene of 20 to 45 mol%, preferably 25 to 35 mol%, and vinyl alcohol of 80 to 55 mol%, preferably 75 to 65 mol%. Usually, a copolymer of ethylene (20 to 45 mol%) and vinyl acetate (80 to 55 mol%) is treated with an alkali such as caustic soda or caustic so that the saponification degree is 86 mol% or more, preferably 90% or more. ~ 100
It is obtained by hydrolyzing so that the content becomes%.

When the proportion of vinyl alcohol in the copolymer is less than 55 mol%, the adhesive force with the inorganic oxide vapor deposition layer is insufficient. On the contrary, when it exceeds 80 mol%, the stretchability of the film is impaired. The melting point of the ethylene / vinyl alcohol copolymer is 178 to 205 ° C. The coating liquid of the ethylene / vinyl alcohol copolymer is prepared by adding the ethylene / vinyl alcohol copolymer to water or a mixed liquid of water and an alcohol such as ethylene alcohol or isopropylene alcohol to have a resin solid content of 5 to 50% by weight. It is obtained by dissolving so that

Various additives such as an emulsifier, an antistatic agent, an antiblocking agent, and a viscosity modifier can be appropriately added to the coating liquid according to the purpose. The viscosity of the coating solution is 10 at 20 ° C.
5,000 centipoise, 300-60,000 at 40 ° C
It is 0 centipoise (B-type viscometer). Application of the coating liquid of the ethylene / vinyl alcohol copolymer to the base layer film is performed by, for example, a gravure roll method, an inverse roll method,
Various coating methods such as a reverse roll method, an air knife coating method, a metalling bar coating method, or a combination thereof can be adopted.

The thickness of application is 10 to 60 in terms of wet film thickness.
In the range of μ, the thickness of the final stretched product is selected to be 0.05 to 4 μm. The coating liquid used for coating is preferably heated to 60 to 100 ° C. before use. 60 ° C
If it is less than 100, it is difficult to maintain the proper viscosity of the coating solution of ethylene / vinyl alcohol copolymer, so it is difficult to obtain a uniform coating. If it exceeds 100 ° C, the solvent in the coating solution of ethylene / vinyl alcohol copolymer evaporates. However, the viscosity becomes too high, making uniform coating difficult.

Method for Producing Laminated Stretched Film In the gas barrier film of the present invention, the above-mentioned olefin resin is melt-extruded into a film in a single layer or a multilayer, and the unstretched film is subjected to a peripheral speed difference between roll groups or a tenter. After stretching in the machine direction 2 to 7 times in the longitudinal direction, the stretched film is heated and subjected to a corona discharge treatment of 30 to 100 w · min / m ² and the corona-treated surface of the longitudinally stretched film is treated with ethylene / vinyl alcohol. After coating with a coating solution of the polymer, after drying, it is stretched in the transverse direction 3.5 to 12 times with a tenter, and further 30 to 100 w · min / min on this coating surface
It is manufactured by performing a corona discharge treatment of m ² . If the amount of corona discharge treatment before and after the above is less than 30 w · min / m ² , pinholes are generated in the coating film of the ethylene / vinyl alcohol copolymer resin, and a uniform coating film cannot be obtained.

On the other hand, when it exceeds 100 w · min / m ² , discharge sparks are large and a whitening pattern is formed on the coating film, which causes uneven coating. For heating before the corona discharge treatment, a heating metal roll, a hot air oven, a far infrared heater or the like is used. The first-stage heating is 60 to 100 ° C, and the second-stage heating is 20 to 11
The temperature is 0 ° C, preferably 80 to 110 ° C. If the amount of corona discharge treatment in the latter stage is less than 30 w · min / m ² , the adhesion between the ethylene / vinyl alcohol copolymer resin layer and the inorganic oxide vapor deposition film layer will be poor, and if it exceeds 100 w · min / m ² , blocking will occur. It is easy to cause uneven whitening of the film, resulting in poor appearance.

The laminated stretched film has a base material layer having a thickness of 10 to 10.
It is a laminate of a uniaxially stretched film of an ethylene / vinyl alcohol copolymer having a thickness of 0.05 to 4.0 μm and a biaxially stretched polyolefin film of 100 μm in thickness. The total thickness of the laminated resin film is 10.05 to 104 μm, and the transparency is 5% or less, and preferably 1 to 3%, in the degree of haze (JIS K7105).

[0016]Inorganic oxide deposition As the thin film on which the inorganic oxide is deposited, SiO is used._x, SnO
_x, ZnO_x, IrO _x200-4,000 ang of etc.
Strom, preferably 300-3,000 angstroms
ROHM's one is used. Vapor deposition film thickness 200-4
000 Å is for transparency, deposition rate, gas bar
It is restricted by the rear property and the film winding property.

As the vapor deposition method, a high frequency induction heating method is used.
Molded product under vacuum (1 x 10 ^-8~ 1 × 10⁶toe
Method for depositing an inorganic oxide (Japanese Patent Publication No. 53-129).
No. 63); volatilized in a vapor deposition machine which was evacuated and evacuated in advance.
Gas flow containing organosilicon compounds, oxygen and inert gas
To generate plasma by magnetron glow discharge
SiO_xMethod of depositing the
Kai 64-87772, USP 4,557,946
No., USP 4,599,678) and the like. Also, 19
Industrial materials published in November 1990, Vol. 38, No. 14
Pages 104-105, ion plating method, high frequency
Plasma CVD method, electron beam (EB) vapor deposition method, spatter
It is classified as the Taling method and its principle is introduced.
It

[0018]

The present invention will be described in detail below with reference to examples, but the scope of the present invention is not particularly limited thereby. Example 1 Using an extruder, polypropylene (MFR 2.3 g / 10
Min, melting point 164-167 ° C.) melt the resin at 210 ° C.,
The sheet was extruded from a T-die and cooled to 60 ° C. to obtain an unstretched sheet. This unstretched sheet was stretched 5 times at a temperature of 130 ° C. by a longitudinal stretching machine composed of a group of heating rolls having different peripheral speeds, and then this longitudinally stretched sheet was heated to 90 ° C.
Then, the surface side to be coated was subjected to corona discharge treatment under the condition of 90 w · min / m ² .
Next, ethylene (29 mol%)-vinyl alcohol (71 mol%) random copolymer resin (Nippon Gosei Kagaku Kogyo Co., Ltd. Soarnol 30L (trade name); melting point 188 ° C.) coating liquid (resin concentration) heated to 80 ° C. 30% by weight) was coated to a thickness of 15 μm with a metalling bar coater, introduced into a tenter oven at 155 ° C. via a conveying roller, stretched 10 times in the transverse direction, and heat set at 160 ° C. Then, this film was heated to 105 ° C., and a corona discharge treatment was applied to the coated surface so that the corona treatment amount was 50 w · min / m ^2, and a coating film having a thickness of 20 μm (coat layer thickness 0.45 μm) was obtained. Obtained.

This film was applied to a plasma deposition device (BP
-1; Samco International Laboratories), and the inside of the apparatus under reduced pressure of 1.33 × 10 ⁻⁴ Pa, hexamethyldisiloxane 3 parts by volume, oxygen 3 parts by volume, helium 20 parts by volume, argon 13 The mixed gas in the capacity part was introduced into the apparatus, and glow discharge was performed from the unbalanced magnetron to generate plasma to deposit SiO ₂ . This SiO
₂ The oxygen permeability of the vapor-deposited laminated stretched resin film was measured.

Example 2 Polypropylene (MFR 2.3 g / 10 min; melting point 165)
~ 170 ° C) resin and adhesive resin; maleic anhydride (0.
35% by weight) Grafted polypropylene (MFR 3g / 1
0 min; melting point 165 to 170 ° C.) melted at 220 ° C. in separate extruders and fed to one coextrusion die,
Layered in a die and extruded, the following Example 1
In the same manner as above, after stretching 5 times in the longitudinal direction, corona treatment is applied to the adhesive resin side, ethylene-vinyl alcohol random copolymer resin coating liquid is coated, and after stretching 10 times in the transverse direction, corona discharge treatment is applied, A stretched film having a thickness of 20 μm was obtained. This film was coated with SiO _{2 in the same} manner as in Example 1.
Was vapor-deposited and the oxygen permeability was measured.

Comparative Example 1 A biaxially stretched film was produced in the same manner as in Example 1 except that the coating liquid of ethylene / vinyl alcohol copolymer resin was not applied and the corona discharge treatment in the previous stage was not performed, and SiO _{2 was used.}
Was vapor-deposited and the oxygen permeability was measured. Comparative Example 2 A biaxially stretched film was produced in the same manner as in Example 1 except that the biaxially stretched film SiO ₂ was not deposited, and the oxygen permeability was measured.

Evaluation (1) Change with respect to secondary processing The SiO ₂ vapor-deposited surface of the biaxially stretched films obtained in Examples 1 and 2 and Comparative Examples 1 and ₂ or before corona discharge treatment,
Using a laminator apparatus, MFR is 5 g / 10 min, a low density polyethylene having a density of 0.922g / cm ³ 320 ℃
Was extruded from a T-die into a film having a thickness of 20 μm and laminated. The oxygen transmission rate of this laminate is shown in Table 1.

(2) Change with respect to external stress The biaxially stretched films obtained in Examples 1 and 2 and Comparative Examples 1 and 2 and the laminated film with low density polyethylene were used in a gelbot tester manufactured by Meitetsu Keiki Co., Ltd. After the film was rolled into a tubular shape, both ends of the tubular tube were fixed to a gripping device of a tester, and a twist of ± 90 ° was repeated 10 times, and then the oxygen transmission rate was measured. The measured values are shown in Table 1.
Shown in.

[0024]

[Table 1]

[0025]

INDUSTRIAL APPLICABILITY The biaxially stretched film on which the inorganic oxide is vapor-deposited according to the present invention is a resin molded product which does not deteriorate in gas barrier property even when heat or force is applied during secondary processing or during use.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C09D 129/04 PEV C23C 14/10 8939-4K // B29K 23:00 B29L 9:00

Claims (1)

[Claims] 1. An unstretched film obtained by melt-extruding an olefin resin is stretched in the machine direction, and then 60-100.
℃ heated to perform the corona discharge treatment of 30～100W · min / m ^2, and then the ethylene content in the corona-treated surface of the vertical oriented film is 20 to 45 mole percent ethylene - a coating liquid of a vinyl alcohol copolymer After coating and drying, stretch in the transverse direction with a tenter,
A gas barrier property of a structure in which a vapor-deposited film of an inorganic oxide is formed on the stretched film surface of the ethylene-vinyl alcohol copolymer of the laminated stretched film obtained by performing a corona discharge treatment of about 100 w · min / m ² Resin molded products.