JPS61204239A - Surface-treatment of polypropylene resin - Google Patents

Abstract

PURPOSE:To improve the adhesivity, paintability, printability, etc. of the titled resin, remarkably, easily at a low cost, without necessitating an expensive high-vacuum apparatus, by carrying out the corona discharge treatment of a specific polypropylene resin under a specific condition. CONSTITUTION:A propylene copolymer containing ethylene component, or a mixture of a propylene polymer and an ethylene polymer is used as the polypropylene resin, and the resin is subjected to corona discharge treatment at a temperature above the melting point of the polypropylene resin, preferably at a temperature higher than the melting point by 2-40 deg.C, in an atmosphere having an oxygen-content of <=10vol%. The corona discharge treatment is carried out preferably in an atmosphere of CO2 gas or nitrogen monoxide gas used as the treating gas.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a surface treatment method for polypropylene resin, and more specifically, it has a significant effect of improving the physical properties of polypropylene resin, particularly adhesiveness, paintability, printability, etc. (Moreover, it is a surface treatment method for polypropylene resin that can be performed at low cost with relatively easy operations.

[Prior Art and Problems to be Solved by the Invention] Polypropylene resins have been used as various materials because of their excellent heat resistance, strength, and moisture permeability. However, since polypropylene resin is non-polar and crystalline, its surface properties, particularly adhesiveness, paintability, and printability, are poor, and its use has been limited.

Therefore, various surface treatments have been carried out to improve these surface characteristics. In addition, various methods have been proposed for laminating with other functional materials by improving adhesion through surface treatment and by using adhesives.

Example Eva, (l) A method of treating the surface of a molded product made of an ethylene-containing ethylene-propylene block copolymer or a mixture of polyethylene and polypropylene with low-temperature plasma under conditions of 100 mHg or less (Japanese Patent Application Laid-Open No. 1982-82825), (2 ) A multilayer material consisting of a layer made of a mixture of polyethylene and polypropylene and a polyethylene layer is sprayed with an ozone-containing gas while the polyethylene layer side is in a molten state.
A method of laminating an anchor coated material on this surface (Japanese Patent Publication No. 58-112740), f3) A method of subjecting the film immediately after extrusion to a corona discharge treatment and adhering it to the base material (Japanese Patent Publication No. 1112-1982) ), (41) There is a method in which a corona discharge treatment is performed in advance when bonding polypropylene and ethylene-vinyl alcohol copolymer via a specific adhesive resin (Japanese Patent Application Laid-open No. 15129/1983). However, ( Method 1) requires a high vacuum state,
Equipment costs are high and continuous processing is difficult due to high vacuum.
Method (2) requires anchor coating, which is expensive due to the equipment and process for anchor coating, and
There are safety issues due to anchor coat treatment. Also(
In method 3), the adhesive force was low, and in method (4), an adhesive resin was required, and the level of adhesive strength was also low.

As described above, a fully satisfactory method for improving the surface properties of polypropylene resins has not yet been found.

[Means for solving problems]

Therefore, the present inventors investigated methods for improving the surface properties of polypropylene resins, and found that the objective could be achieved by subjecting a specific resin to a specific treatment.Based on this knowledge, the present inventors developed the present invention. Completed the invention.

That is, the present invention uses a propylene copolymer containing an ethylene component or a mixture of a propylene polymer and an ethylene polymer as the polypropylene resin, and treats the surface of the polypropylene resin at a temperature higher than the melting point of the polypropylene resin. The present invention provides a surface treatment method for a polypropylene resin, which is characterized by carrying out a corona discharge treatment in an atmosphere having an oxygen content of 10% by volume or less.

The polypropylene resin used as a raw material in the present invention is either an ethylene component-containing propylene copolymer or a mixture of a propylene polymer and an ethylene polymer. In the present invention, sufficient effects can be obtained by specifying these raw materials. Here, the ethylene component-containing propylene copolymer is not particularly limited as long as it is a copolymer having an ethylene repeating unit and a propylene repeating unit, and various copolymers can be used.

In particular, the ethylene component content is preferably 2 to 30% by weight, preferably 2 to 20% by weight. Specifically, ethylene-propylene random copolymer.

There is an ethylene-propylene block copolymer.

The melt index (MI) of these ethylene-propylene copolymers is not particularly limited, and is usually 0.1 to 2.
0 g/10 minutes is used.

In addition, mixtures of propylene polymers and ethylene polymers include propylene polymers such as homopolypropylene and ethylene-propylene copolymers, and polyethylene, ethylene-α-olefin copolymers, and ethylene-propylene rubber (EPR). , a terpolymer of ethylene and propylene copolymerized with a small amount of diene (EPDM), and an ethylene-based polymer such as an ethylene-unsaturated acid copolymer may be used. The content of the ethylene component in the ethylene polymer should be 2% by weight or more (there is no particular restriction).In addition, there is no particular restriction on the mixing ratio of the ethylene polymer and propylene polymer. types, uses,
It may be determined as appropriate depending on the desired physical properties. in general,
The blending ratio of the ethylene polymer is 40% by weight or less, preferably 1 to 30% by weight. In any case, in the present invention, if homopolypropylene is used as the polypropylene resin, the object of the present invention cannot be achieved at all. Therefore, it is necessary to contain an ethylene component in the polypropylene resin molded article, and the ethylene component is obtained by mixing a propylene-ethylene copolymer or an ethylene polymer.

The polypropylene resin of the present invention is composed of the above-mentioned copolymer or mixture, but various additives can be added as desired. Additives include titanium, talc, calcium carbonate, barium sulfate, inorganic powders such as clay, stabilizers against oxidation, heat, light, etc., glass fiber,
Reinforcing materials such as carbon fibers, rubbers, lubricants, antistatic agents, plasticizers, colorants, etc. can be added as appropriate.

In the present invention, the above-mentioned raw materials are first thoroughly kneaded and then molded into various shapes using a conventional molding method. Molding is generally done by extrusion, and forms membrane-like films,
It is formed into a sheet or other desired irregular shape. here,
When formed into a film or sheet, it may be multilayer coextruded with other resins, or may be lined with aluminum foil or other heat-resistant resin sheet 1 if necessary.

Next, the resin thus formed into a shape such as a film-like object or an irregularly shaped object is subjected to a corona discharge treatment.

Here, the corona discharge treatment is performed at a temperature higher than the melting point of the polypropylene resin in an atmosphere with an oxygen content of 10% by volume or less.

The temperature above the melting point of the polypropylene resin is the temperature at which the resin is in a molten state, and is 1 to 60 degrees higher than the normal melting point.
℃, preferably about 2 to 40℃ higher temperature is suitable.

That is, in the case of molding by extrusion molding, if the surface of the molded product is maintained at a temperature equal to or higher than the melting point, corona discharge can be continuously performed as it is.

If the temperature is lower than the melting point, it may be reheated to a temperature higher than the melting point and then subjected to corona discharge treatment. In the case of a sheet or film, reheating may be performed using a heating roll, radiation heating, hot air heating, or the like.

Furthermore, in the case of a lined film, it is sufficient to heat only the side to be treated. In any case, the processing temperature of the present invention may be such that the temperature of the processing surface is equal to or higher than the melting point of the polypropylene resin, and the processing equipment is suitable.

The most suitable method may be selected depending on the process.

In this way, corona discharge treatment is performed on the surface of the molded article at a temperature above the melting point. This treatment must be carried out in an atmosphere with an oxygen content of 10% by volume or less. Methods of performing corona discharge treatment under such an atmosphere include a method of performing corona discharge treatment in a gas atmosphere treatment tank containing carbon dioxide gas, dinitrogen oxide gas, water, air, argon, helium, etc., or a method of performing corona discharge treatment on a surface treated with corona discharge. Examples include a method of performing corona discharge treatment while blowing gas as described above. Here, carbon dioxide gas and dinitrogen oxide gas are particularly preferred as the processing gas, but a mixture of these gases with air and an oxygen content of 10% by volume can also be used.

In the present invention, oxygen in the atmosphere is 10% by volume or less,
Preferably, it may be contained in an amount of 5% by volume or less.

Here, if the oxygen content is too high, the effects of the present invention cannot be fully achieved.

In corona discharge treatment, a high voltage is applied between a grounded dielectric-coated roll or a dielectric-coated metal plate and a knife-shaped electrode that is placed in a gap for several days to discharge corona. This is done by running the sheets. Processing conditions may be arbitrarily determined depending on the processing effect, purpose, etc.

Specifically, in the case of a resin sheet, the treatment method of the present invention described above can be carried out using the apparatus shown in FIG. That is, the sheet 4 extruded from the die exit of an extrusion molding machine and having a temperature higher than the melting point is directly extruded into a predetermined gas atmosphere chamber 1, then subjected to a predetermined amount of corona discharge treatment by a corona discharge treatment device 2, and then cooled 2. A surface-treated resin sheet can be obtained by winding or other methods. Here, as the processing device 2, for example, a pair of ceramic electrodes is used.

The surface of the film-like object or the irregularly shaped object subjected to the corona discharge treatment has excellent adhesion, paintability, printability, etc.

Therefore, a laminate or a laminate can be easily produced with a material different from the polypropylene resin and with high adhesive strength. As such materials, single-layer or multi-layer sheets or films made of functional materials such as ethylene-vinyl alcohol copolymer, polyamide, polyvinylidene chloride, and polyester are preferable. Examples include a laminate.

By laminating such a material with the corona discharge treated surface of a sheet or film made of a polypropylene resin treated with corona discharge as described above, a laminate consisting of two or more layers can be produced. The material to be laminated with the corona discharge treated polypropylene resin does not need to be corona discharge treated, but may be corona discharge treated. Also,
It is preferable to heat the above-mentioned materials before laminating them.

Lamination is usually carried out at a temperature higher than the melting point of the polypropylene resin, preferably 2 to 10° C. higher than the melting point.

For example, when manufacturing a laminate, if the apparatus is used as shown in FIG. 2, the laminate can be manufactured continuously and efficiently with high adhesive strength.

That is, a resin sheet 4 and a sheet 5 made of another material are each introduced into a predetermined gas atmosphere chamber 1 by guide rolls,
The polypropylene resin is subjected to a corona discharge treatment using the corona discharge electrode 2A, and if necessary, the sheet 5 is also subjected to a corona discharge treatment, and the treated surfaces are laminated to obtain a laminate 6. Here, the surface of the sheet 4 is heated by a heating roll 3 in order to maintain the corona treatment temperature above the melting point of the polypropylene resin.

In addition, when laminating both sheets, it is necessary that the polypropylene resin has a melting point or higher, and although it is preferable that the sheet 5 is heated, the temperature does not need to be higher than the melting point of the resin. As shown in FIG. 1 as the sheet 4 in FIG. 2, corona treatment can also be performed by directly extruding the sheet from a T-die into the processing chamber.

〔Effect of the invention〕

As described above, according to the surface treatment method for polypropylene resin of the present invention, the surface properties of the polypropylene resin as described above, particularly adhesiveness, paintability, printability, etc., are greatly improved. Furthermore, since the high vacuum equipment required in conventional low-temperature plasma processing is not required, this greatly contributes to reducing equipment costs and simplifying processing operations, especially continuous processing. It can be manufactured even higher. That is, since adhesive resin is not required, extrusion equipment and raw materials are not required, and it is also advantageous in terms of molding workability. Furthermore, since surface treatment and anchor treatment of other materials to be laminated are not required, it becomes possible to manufacture the laminate at a lower cost and with high safety.

Therefore, the present invention is extremely useful for improving the surface properties of various molded articles, particularly for producing laminates.

〔Example〕

Next, the present invention will be explained in detail with reference to Examples.

Examples 1 to 8 and Comparative Examples 1 to 3 A polypropylene resin (PP) sheet with a thickness of 300 μm formed by molding a resin made by blending predetermined amounts of each component shown in Table 1, and an ethylene-vinyl alcohol copolymer. (EVO
H) (ethylene content 32 mol%, Mll, 3 g/10
min, density 1.19 g/d.

Melting point 181℃, @Kuraray "EVAL EP-Flol"
) Corona discharge treatment bag shown in Figure 2 is a sheet with a thickness of 200μ! (Heating roll diameter 35 φ, roller + output cuff
000 V,! The mixture was treated for a predetermined time using a cooling roll (50°C), taken off, and subjected to corona treatment, and then heated and pressed using two rolls to obtain a laminate. The peel strength of the obtained laminate was measured.

The results are shown in Table 1.

*1...R-PP: Random polypropylene (ethylene content 3% by weight, M17g/10min, density 0.90
g/c1. Melting point 155°C, Idemitsu Petrochemical side type “Idemitsu Polypro F73ONJ) H-PP: Homopolypropylene (MIo, 6 g/10 min, density 0.91 g/cd,
Melting point 161°C, manufactured by Idemitsu Petrochemical ■ [Idemitsu Polypro E100GMJ] LDPE: Low density polyethylene (Mltg/10 min, density 0.919 g/cd, melting point 111°C, manufactured by Toyo Soda ■ “Vetrocene 172J)” EVOH: Ethylene-vinyl Alcohol copolymer (Mll, 3g/10min, density 1.1
9g/aa, melting point 181℃, ■ "Eval EP" manufactured by Kuraray
-F 101J') EPR: Ethylene-propylene rubber (MlO, 4g/1
Made of 0 minute 2 Japanese synthetic rubber ■.

rJSREPO7J) *2: Indicates capacity ratio.

*3...Compliant with JIS K6854

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of an apparatus for implementing Process J method of the present invention, and FIG. 2 shows a schematic diagram of an apparatus for manufacturing a laminate using Process 1 method of the present invention. 1... Gas atmosphere chamber in the absence of oxygen gas. 2A, 2B...Corona discharge electrode, 3...Heating roll. 4...Polypropylene resin sheet. 5...Resin sheet of other material, 6...Laminated body 7...
・Corona discharge power source Figure 1 Figure 2 Procedural amendment stamp button April 2, 1985

Claims (3)

[Claims] (1) When treating the surface of polypropylene resin, use a propylene copolymer containing an ethylene component or a mixture of a propylene polymer and an ethylene polymer as the polypropylene resin, and add oxygen at a temperature higher than the melting point of the polypropylene resin. A method for surface treatment of polypropylene resin, characterized by subjecting it to corona discharge treatment in an atmosphere of 10% by volume or less. (2) The surface treatment method according to claim 1, wherein the ethylene component content in the ethylene component-containing propylene copolymer is 2 to 30% by weight. (3) The surface treatment method according to claim 1, wherein the ethylene polymer content of the mixture of propylene polymer and ethylene polymer is 40% by weight or less.