JP2005213454A - Polyolefin resin molded product, method for producing the same and laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently provide polyolefin resin molded product that has excellent adhesion to coating film, adhesive, ink and the like and retains mechanical properties. <P>SOLUTION: This is a polyolefin resin molded product in which acrylic resin is dispersed on at least a part of the surface but the acrylic resin does not disperse inside the resin. In this method for producing the polyolefin resin molded product, the molded product of polyolefin resin is impregnated with a (meth)acrylic ester so that the acrylic ester may be soaked into the amorphous phase on the surface of the molded product in the supercritical carbon dioxide and then the soaked (meth)acrylic ester is polymerized. The polymerization is preferably carried out by photopolymerization. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyolefin resin molded product that can be easily painted and printed.

  Polyolefin resins are widely used in various applications because they are excellent in mechanical properties and chemical resistance, are low in cost, and have good moldability. In addition, since the polyolefin resin is excellent in recyclability, it is an environmentally friendly resin.

  However, since the polyolefin-based resin is nonpolar, the adhesion between the molded product made of the polyolefin-based resin and the coating film, adhesive, ink, or the like is not good. Therefore, as a method for increasing the adhesion, there is a method of activating the surface of a molded article made of polyolefin resin by subjecting it to a surface treatment such as plasma treatment, flame treatment, ultraviolet irradiation treatment, chromic acid treatment, etc. .

  However, such surface treatment has a drawback that a uniform surface treatment effect cannot be obtained due to the shape and size of the molded product and the influence of dyes, pigments and additives contained in the polyolefin resin.

  On the other hand, as a method of coating a molded product made of polyolefin resin without surface treatment, a chlorinated polyolefin resin having a strong adhesion to the polyolefin resin is used as a primer (lower layer of the coating). A method of using an acrylic resin or the like as a top coat (upper layer of coating) is known (see Patent Document 1). Patent Document 1 discloses a resin composition having a weight ratio of 10:90 to 90:10 of a chlorinated polyolefin resin and an acrylic copolymer as a primer.

  However, the use of chlorine-containing compounds tends to be avoided due to increased interest in environmental problems. For this reason, primers that do not contain chlorine are also disclosed, but these primers may be made of a copolymer of expensive monomers (see, for example, Patent Document 2).

Also disclosed is a method for producing an incompatible PP / PMMA dispersion by impregnating and polymerizing methyl methacrylate (MMA) on isotactic polypropylene (PP) in a supercritical carbon dioxide fluid (non-patent document). 1). However, in the dispersion system, since PMMA is dispersed inside the PP, the mechanical properties of the PP are changed without being maintained. Moreover, productivity is inferior because methyl methacrylate is thermally polymerized.
Japanese Examined Patent Publication No. 63-24628 JP 2003-238889 A Polymer Preprints, Japan vol. 52, no. 9 (2003), p1825-1826

  An object of the present invention is to efficiently provide a polyolefin-based resin molded article that has high adhesion to a coating film, an adhesive, an ink, etc. and maintains mechanical properties without using a compound containing a chlorine atom. It is in.

  The gist of the present invention resides in a polyolefin resin molded product in which an acrylic resin is dispersed on at least a part of the surface, and the polyolefin resin molded product in which the acrylic resin is not dispersed therein.

  Further, the gist of the present invention is that the above-mentioned polyolefin resin molded article is obtained by impregnating a amorphous phase on the surface of a molded article made of polyolefin resin in supercritical carbon dioxide and polymerizing it. It is in the manufacturing method.

  The polyolefin resin molded article of the present invention has good adhesion to a coating film, an adhesive, ink, and the like, and the mechanical properties of the polyolefin resin are maintained.

  Hereinafter, the present invention will be described in detail.

  Examples of the polyolefin resin constituting the polyolefin resin molded article of the present invention include low density polyethylene, ultra low density polyethylene, linear low density polyethylene, high density polyethylene, ultra high density polyethylene, polypropylene, ethylene-propylene copolymer, Polymethylpentene, propylene-butene-1 random copolymer, propylene-ethylene-butene-1 random copolymer, copolymer of propylene and α-olefin having 5 to 12 carbon atoms, ethylene-nonconjugated diene copolymer Polymer, propylene-nonconjugated diene copolymer, polybutene, ethylene-vinyl acetate copolymer, ethylene-vinyltrimethoxysilane copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene -Methyl methacrylate copolymer . Moreover, these can also be used together.

  In order to make these polyolefin resins into a desired shape, general resin molding processing methods such as injection molding, hot press molding, extrusion molding, and inflation molding can be used.

  In the polyolefin resin molded article of the present invention, the acrylic resin is dispersed on at least a part of the surface thereof, and the acrylic resin is not dispersed inside thereof.

  The dispersed acrylic resin may be a general (meth) acrylic acid ester homopolymer, copolymer, or a copolymer thereof with styrene, butadiene, isoprene, or the like. “(Meth) acryl” means “acryl” or “methacryl”.

  In the present invention, “the acrylic resin is dispersed on at least a part of the surface” means that the acrylic resin is dispersed on the surface of a molded article made of a polyolefin resin on the order of submicron or less. When the surface area to which the coating film, adhesive, ink and the like are adhered is 100%, the surface area in which the acrylic resin is dispersed is preferably 10 to 90%, and more preferably 30 to 70%. The acrylic resin is preferably dispersed in the amorphous phase of the polyolefin resin.

  In the polyolefin-based resin molded product of the present invention, “the acrylic resin is not dispersed therein” means that the distance from the surface of the polyolefin-based resin molded product in which the acrylic resin is dispersed to another surface facing it. It means that the acrylic resin is not dispersed at a location exceeding 1/10 distance from the surface. For example, in the case of a resin plate having a thickness of 7 mm, the acrylic resin is not dispersed in the interior exceeding the depth of 0.7 mm from the surface where the acrylic resin is dispersed. If the acrylic resin is dispersed to the inside, it is not preferable because the mechanical properties of the polyolefin resin are not maintained and change.

  On the other hand, if the acrylic resin is dispersed not only on the surface of the polyolefin resin molded product but also to a certain depth from the surface, the adhesion between the polyolefin resin molded product and the coating film, adhesive, ink, etc. is further improved. Therefore, it is preferable.

  For example, in terms of adhesion to the ink, the depth from the surface where the acrylic resin is dispersed is sufficient for the polyolefin resin to exceed 3 mm in order to maintain the mechanical properties of the polyolefin resin. Even if it has, it is preferable that it is the depth to 300 micrometers from the surface. A depth of up to 10 μm is more preferable, and a depth of up to 5 μm is more preferable from the efficiency of producing a polyolefin resin molded product.

  The dispersion state of the acrylic resin in the polyolefin resin molded product can be confirmed with an electron microscope. Specifically, a test piece of an appropriate size is cut out from the surface of the polyolefin resin molded product. A sample having a thickness of 0.1 to 0.2 μm including the surface is cut out from the test piece with a microtome, and the state of dispersion on the surface can be confirmed by observing the surface with a transmission electron microscope. Further, a sample having a thickness of 0.1 to 0.2 μm is cut out from the test piece along the thickness direction of the polyolefin-based resin molded article with a microtome, and the cut surface is observed with a transmission electron microscope, so that the inside from the surface is observed. The dispersion state of the acrylic resin can be confirmed.

  Acrylic materials are often used for paints, adhesives, inks, and the like, which are raw materials for the coating film. These materials do not have good adhesion to polyolefin resins, but have good adhesion to acrylic resins. Therefore, the polyolefin resin molded product of the present invention in which an acrylic resin is dispersed on the surface thereof and the coating film, adhesive, ink, etc. have good adhesion.

  Adhesion with paint film and ink is evaluated by the adhesion rate (number of cells remaining on the substrate) of the paint film or ink on the substrate cut into goby eyes (1 mm interval, 100 squares) by the cellophane tape peeling test. (JIS K 5400).

  As a method for producing a polyolefin resin molded product in which an acrylic resin is dispersed on at least a part of the surface of the present invention, first, a polyolefin resin is molded by a known resin molding method, and a (meth) acrylic ester is used. And the polymerization phase initiator is immersed in supercritical carbon dioxide, and the amorphous phase on the surface of the molded article made of polyolefin resin is impregnated with (meth) acrylic acid ester and the polymerization initiator. A method of polymerizing a (meth) acrylic acid ester is mentioned. Supercritical carbon dioxide is carbon dioxide under temperature and pressure above the critical temperature and pressure.

  The depth of impregnation of the (meth) acrylic acid ester into the molded product made of polyolefin resin in supercritical carbon dioxide is determined by the time, pressure, and temperature of impregnation with supercritical carbon dioxide. The temperature and pressure are not particularly limited as long as carbon dioxide is in a supercritical state, and the temperature may be 32 ° C. or higher and the pressure may be 7.7 MPa or higher. Although the upper limit is determined by the equipment, the temperature is preferably 50 ° C. or lower and the pressure is preferably 10 MPa or lower in view of energy efficiency. The higher the temperature and the higher the pressure, the shorter the impregnation time, but the impregnation time is preferably 1 minute or more and 1 hour or less. If the impregnation time is too short, the impregnation depth becomes shallow, which is not preferable. If the impregnation time is too long, the (meth) acrylic ester is impregnated into the molded product made of polyolefin resin, which is not preferable, and is not preferable from the viewpoint of productivity.

  Examples of the (meth) acrylate ester to be impregnated include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth ) T-butyl acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like. A (meth) acrylic acid ester may be used in combination with a diene monomer such as butadiene, isoprene or chloroprene, or a styrene monomer such as styrene or α-methylstyrene. In order to obtain good adhesion to a coating film, adhesive, ink, etc., it is preferable to use a monomer similar to the monomer in the resin constituting them.

  As the polymerization initiator, a general radical polymerization initiator or photopolymerization initiator can be used. As the radical polymerization initiator, an organic peroxide or an azo compound is usually used. When a radical polymerization initiator is used as the polymerization initiator, the (meth) acrylic acid ester is polymerized by heating after impregnation. The polymerization temperature is preferably not higher than the melting point of the molded article made of polyolefin resin, and more preferably 50 to 80 ° C., within the range where the used radical initiator is decomposed. If the melting point is higher than the melting point, the crystal structure of the molded product is destroyed, which is not preferable.

  The amount of the radical polymerization initiator is preferably in the range of 0.001 to 10 parts by mass, more preferably in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the monomer containing (meth) acrylic acid ester. More preferably within the range of 0.1 to 3 parts by mass. If the radical polymerization initiator is too small, the polymerization reaction may not proceed smoothly, and if it is too large, molecular cleavage of the polyolefin-based resin molded product may easily occur.

  On the other hand, the use of a photopolymerization initiator as the polymerization initiator is preferable from the viewpoint of productivity because the temperature of the molded article does not increase and the polymerization time is short. When a photopolymerization initiator is used, the light for initiating polymerization does not reach the deep part of the molded article made of polyolefin resin, so that the impregnation of (meth) acrylate is preferably 5 μm or less from the surface.

  A photopolymerization initiator absorbs ultraviolet rays to initiate a polymerization reaction. And methyl uranium monosulfide and thioxanthones.

  It is preferable that the usage-amount of a photoinitiator is 0.1-10 mass parts with respect to 100 mass parts of monomers containing (meth) acrylic acid ester. If the amount is too small, the polymerization reaction may not proceed smoothly. When the amount is too large, the irradiation amount of ultraviolet rays is insufficient, and an unreacted photopolymerization initiator may remain, which is not preferable.

A photopolymerization initiator having a maximum absorption wavelength of 320 to 380 nm is preferable because it is easy to handle. The light used for the polymerization depends on the kind of the polymerization initiator, but light including a wavelength of 300 to 400 nm is preferable from the viewpoint of handleability. It is preferable to measure it with an illuminometer for light measurement near a wavelength of 350 nm and use it as energy to irradiate 1 to 1000 mJ / cm ² . As the light source, a mercury lamp, a metal halide lamp, a chemical lamp, or the like can be used.

  When impregnated with (meth) acrylic acid ester, various stabilizers such as antioxidants, ultraviolet absorbers and heat stabilizers, and colorants such as pigments may be impregnated as necessary.

  The polyolefin resin molded product in which an acrylic resin is dispersed on at least a part of the surface of the present invention has good adhesion to a coating film, an adhesive, ink, and the like. In addition, since the acrylic resin is not dispersed inside the polyolefin resin molded product, the mechanical properties of the polyolefin resin molded product are maintained.

  Laminated products having a coating layer cured by applying a paint on the surface of the polyolefin resin molded product of the present invention are suitable for accessories, vehicle parts, etc. such as accessory cases, pencil stands, CD racks, letter cases, etc. is there. In particular, a laminated product made of a polypropylene resin molded product having a coating film mainly composed of an acrylic resin is suitable for an automobile bumper. A general method is used for applying the paint. For example, there is a method of spraying and applying paint with a spray gun.

  Since the polyolefin-based resin molded product of the present invention has good adhesion to an adhesive, it can be attached with a seal or the like, and is suitable as the aforementioned sundries.

  The film printed with the ink on the polyolefin-based resin molded product of the present invention is suitable for a packaging film or the like that requires design. In particular, a polypropylene resin film printed with an ink mainly composed of an acrylic resin is suitable. As a printing method, a general printing method such as gravure printing or offset printing is used.

  The polyolefin resin molded article of the present invention is useful as a bumper for automobiles or a film for packaging.

Claims (6)

  A polyolefin resin molded product in which an acrylic resin is dispersed on at least a part of a surface thereof, and an acrylic resin is not dispersed in the polyolefin resin molded product.   A laminate having a coating layer on the surface of the polyolefin resin molded product according to claim 1.   An automobile bumper comprising the laminate according to claim 2.   The packaging film formed by printing on the surface of the polyolefin-type resin molded product of Claim 1.   The method for producing a polyolefin resin molded article according to claim 1, wherein the amorphous phase on the surface of the molded article made of a polyolefin resin is impregnated with superpolymer in a supercritical carbon dioxide and then polymerized.   The method for producing a polyolefin resin molded article according to claim 5, wherein (meth) acrylic acid ester is polymerized by photopolymerization.