JPS62174246A - Polymer composition and molding having improved heat resistance - Google Patents

Abstract

PURPOSE:To provide a polymer compsn. which has excellent heat resistance, flexibility and adhesion to coating films and gives moldings for exterior finish materials for automobile which an be coated and baked, consisting of two ethylene/vinyl acetate copolymers having different vinyl acetate contents and PE and/or an ethylene/alpha-olefin copolymer. CONSTITUTION:50-85% (by weight; the same applies hereinbelow) ethylene/vinyl acetate copolymer (A) having a vinyl acetate content of 3-15% is dry-blended or melt-blended with 5-40% ethylene/vinyl acetate copolymer (B) having a vinyl acetate content of 25-45%, 5-25% PE such as a medium-density PE having a density of 0.930g/cm<3> or above, a high-density PE or a linear low- density PE having a density of lower than 0.930g/cm<3>, etc. and/or ethylene/alpha- olefin copolymer (C) and optionally, a filler, colorant, an antioxidant, a weathering stabilizer, etc., (D) to obtain a polymer compsn. having a vinyl acetate content of 8-15%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to polymer compositions. More specifically, the present invention relates to an ethylene-vinyl acetate comonomer composition with improved heat resistance. The present invention also relates to a molded article formed from this ethylene-vinyl acetate copolymer composition, which has improved heat resistance and can be baked and painted.

[Problems to be solved by conventional technology and invention]

Ethylene-vinyl acetate copolymer (hereinafter sometimes abbreviated as EVA) has excellent flexibility, toughness, lightness, and moldability, and these physical properties can be improved by changing the vinyl acetate content in the copolymer. Since it has the advantage of being able to adjust the temperature to a desired level, it has been widely used in fields such as foaming, general molding, films, laminates, and sheets. For example, in the field of foaming, highly crosslinked foams produced by pressing methods or non-crosslinked low foams produced by injection molding methods are used for flip-flops, sole materials for women's footwear, and the like. In the case of general molding, EVA molded products are used in a wide variety of fields, from industrial applications to daily necessities. Typical products include power insulation covers, automobile interior parts, sash gaskets, artificial turf mats, ski shoes, and cushioning. Examples include wood. Furthermore, in the film, laminate, and sheet fields, [iiVAg shaped products are used in food packaging, agricultural materials, and various industrial applications.

Furthermore, since molded products containing Riki-Zen Black have excellent weather resistance, they are also used as exterior parts of automobiles, such as mudguards and bumper protectors.

However, in the market, there is competition with other materials other than EVA, and customer demands for molded products are becoming more diverse and strict.
At present, there is a strong desire to improve the physical properties of WA.

For example, in order to enhance the decorativeness of automobile exterior parts, which have conventionally been mainly painted in black, there is a growing demand for them to be painted in the same color as those used by military vehicles, or to be marked with hot stamps. ing.

In response to this demand, conventional KVA has the disadvantage that molded products are deformed by heating during the paint baking process at 80° C. for 30 minutes, for example, due to insufficient heat resistance.

There was. As a countermeasure, it has a relatively high melting point.

EVA with low vinyl acetate content? If used.

It has the disadvantage that the important adhesion of the coating film is impaired, and there is no version A that satisfies both the adhesion of the coating film and the heat resistance of the molded product.

In addition, in the painting process for polypropylene soles, such as polypropylene cleft pants, in order to remove stains such as mold release agents adhering to the surface of the molded product and obtain stable coating adhesion. Trichloroethane steam cleaning is generally performed as a pretreatment step. When this trichloroethane steam cleaning was applied to an EVA molded product, the surface of the KVA molded product was roughened and became noticeably uneven, making it impossible to obtain a smooth and glossy coating.

For this reason, olefinic thermoplastic elastomers and thermoplastic urethane resins, which are more expensive than EVA, are used as coating resins for exterior parts such as mudguards and pants protectors; There is a strong need to improve the paintability of EVA.

In addition, similar to painting, hot stamping involves heating the molded object to semi-melt the surface and then applying instant pressure to transfer it onto the metal foil. There is a need for EVA that does not undergo thermal deformation even when transferred.

[Means for solving problems]

The present inventor has solved the problem of physical properties, r.
As a result of intensive research into ways to improve the heat resistance of f, we have found that we can solve this problem by using as raw materials a polymer composition consisting of two specific types of EVA with different vinyl acetate contents and a specific ethylene polymer. I hope to find something that can be solved effectively.

Therefore, the present invention provides (4) ethylene containing 3 to 15 parts vinyl acetate.
Vinyl acetate copolymer 5o to 85wt @) Ethylene with a vinyl acetate content of 25 to 45wt and 3%
Vinyl acetate copolymer 5 to 40 weight 1 weight (C) Polyethylene and/or ethylene-α-
The polymer composition is composed of 5 to 25% by weight of an olefin copolymer, and the vinyl acetate content of the composition is 8 to 15% by weight. The present invention provides It, molded from the above composition,
It also relates to molded products with improved heat resistance.

The (4) component EVA having a low vinyl acetate content used in the present invention has a vinyl acetate content of 3 to 15%, preferably 5 to 12%. Physical properties of components (B) and (C).

Although it is related to the blending ratio, in general, if the vinyl acetate content is less than 30%, the molded product becomes hard and has poor cold impact resistance, as well as poor adhesion to the coating film. -If the vinyl acetate content exceeds 15%, even if you try to improve the heat resistance by adding component Q (as described below), only a hard molded product will be obtained due to the increased amount of component Q, which will reduce the characteristics of EVA. It becomes difficult to improve heat resistance while maintaining a certain degree of flexibility.

The EVA component (B) with a high vinyl acetate content used in the present invention has a vinyl acetate content of 25 to 45%, preferably 27 to 35%. Vinyl acetate content is 25%
When the amount is less than that, the effect of improving the adhesion of the coating film is poor, and the effect of imparting flexibility to the molded product is poor. On the other hand, if the vinyl acetate content exceeds 45% gold, the moldability will be poor, for example, the adhesion to the mold during injection molding will be strong, and if the mold release property is poor or significant, the molded product itself will become sticky. The polyethylene and/or ethylene-α-olefin copolymer used in the present invention (component Q is an ethylene homopolymer or glopylene, gutene, heptene, 4-methyl-inten- It is a copolymer of α-olefins having 3 to 8 carbon atoms, such as 1, octene.

Component (C) does not significantly impede the heat resistance obtained by the combination of both components (A) and (B), and furthermore, when trichloroethane vapor treatment is performed as a pretreatment for painting, the surface of the molded product may become noticeably uneven. It is necessary to use an ethylene homopolymer or copolymer that does not cause any stains and gives a smooth and glossy appearance after painting. Variants include high-density, medium-density, low-density polyethylene, linear low-density polyethylene, and ethylene.
These include propylene copolymer plum. Among these polymers,
From the viewpoint of improving the heat resistance of the molded product, high density, medium density and linear low density polyethylene are preferred, especially those with a density of 0.930
Polymers with g/α3 or more are most preferred.

The blending ratio of components (4), (B) and (0) is (4) component 50-85 weight, t%, (B) component 5-40 weight coefficient weight 0
When the component is 5 to 25% by weight, the vinyl acetate content of the composition is 8
~151 ft%. Furthermore, since the polymer composition of the present invention is molded by extrusion molding, injection molding, compression molding, etc.
The melt flow rate (hereinafter abbreviated as MFR) is 0.1
It is preferably in the range of 100 to 100.

If the vinyl acetate content t of the composition is less than 8 inches, the adhesion of the coating film will be poor, and the molded product will be hard and have poor cold resistance. Ten thousand,
If the vinyl acetate content exceeds 15%, heat resistance will be poor.

The polymer composition of the present invention includes fillers such as clay, Merck, calcium carbonate, silica, and partially coated products in which a part of the skin of the bottom surface is directly exposed to the surface. In this case, colorants such as casen black, titanium oxide, organic pigments, or known antioxidants and weathering stabilizers may be added.

Polymer composition of the invention v! ! In order to obtain 11 g, two types of IVA and polyethylene and/or ethylene-α-olefin copolymers are simultaneously or sequentially triblended or melt blended. The tri-blend is mixed using four types of runders, including a Henschel mixer, a tumbler mixer, and a Rigan blender. In the case of a melt blend, it may be mixed using a single-screw extruder, a twin-screw extruder, a pant mixer, etc., and there are no particular limitations.

The nonapolymer composition obtained in this way can be used for thermoforming such as extrusion molding, injection molding, compression molding, etc., to produce automatic military exterior parts such as mudguards and panzer protectors, as well as those mentioned above. It is possible to mold each of the following.

In addition, the process for coating a molded article made from the composition of the present invention as a raw material will be explained below to further clarify the embodiments of the present invention.

In other words, 1. When painting a molded article obtained from the composition of the present invention, first perform a pretreatment.As a small-scale method for degreasing and cleaning the surface of a molded article, white is coated with an organic solvent such as solin or alcohol. There is a method of wiping the surface of the molded product with a solvent, but a method suitable for mass production processes and achieving more stable coating film adhesion is trichloroethane steam cleaning. This trichloroethane steam cleaning involves soaking the molded product in trictetralyethane vapor, condensing on the surface of the cold molded product, and dropping droplets of trichloroethane onto the surface of the molded product to remove dirt on the surface of the molded product. In this method, the surface of the molded product is appropriately roughened to obtain good coating film adhesion. Furthermore, if necessary, a solution containing a partially saponified product of chlorinated polyolefin or ethylene-vinyl acetate resin as a main component can be applied as a primer for painting the 5-layer molded product by dipping or evenly spraying with a spray gun. The surface treatment of the lj EVA molded product is carried out by immersing the molded product in an alcoholic alkaline solution described in JP-A-54-125268.

The paint used for coating EVA is generally a two-component type I diol-curable polyurethane paint consisting of polyisocyanate and polyol.

Polyol bottom valves are polyester polyols, poly(oxypropylene ether)/diol, poly(oxyethylene-
There are polyether polyols such as (propylene ether) polyols, and acrylic polyols that are derivatives of acrylic acid.

As 4-lisocyanate, D@smodur■I
Aromatic polyisocyanates such as L (product of Bayer) and D@smodur[F]L and aliphatic polyisocyanates such as Coronate ML (product of Nippon Ichi Urethane) and D@smodur'N are used. .

Flexible and weather resistant for KVA painting.
For producing polyurethane paints, polyester polyols and acrylic polyols are preferred as the polyol bottom valve, and as the polyisocyanate component, non-yellowing aliphatic polyisocyanates are preferred.

In addition, additives such as amines and organic metal salts are blended as catalysts, oil-soluble dyes and pigments as colorants, water stabilizers, mid-droplet improvers, etc., and aromatic hydrocarbons, esters, or ketones are used as solvents. It is used as a paint.

Although the polyurethane paint may be applied using a brush, a roll coater, etc., spraying W1 is generally performed using a spray gun.

I urethane f applied to EVA! ! L′! + baking is generally performed by heating at 70° C. to 80° C. for 30 minutes to 1 hour.

[Effect]

The polymer composition of the present invention comprises a specific 2ffI EVA having a different vinyl acetate content and a specific polyethylene and/or ethylene-α-olefin copolymer. And molded products made from this composition.

It has excellent physical properties, especially heat resistance, which cannot be obtained with EVA of the phosphor component produced by direct polymerization. To explain this effect using the paintability of molded products as an example, EVA molded products made from the composition of the present invention do not develop significant irregularities on the surface when washed with trichloroethane, and do not impair their appearance. Paint f! ! It is possible to prevent deformation due to heating during the baking process of a coating film that maintains adhesion to LIK.

That is, the composition of the present invention has a low vinyl acetate content.
Two types of EVA: A and 4A with high vinyl acetate content
However, the EVA compound thus obtained has significantly improved heat deformation resistance compared to the 1iVA of the Rin-component obtained by direct polymerization, and the amount of deformation due to its own weight is extremely small. With.

It is characterized in that it contains a polymer that also has a sufficient number of vinyl acetate units, which are polar groups necessary to obtain good adhesion to the coating film.

However, even with the 2-type l1lVA compound obtained in this way, if trichloroethane cleaning is applied as a pretreatment for painting, the surface of the molded product will be significantly roughened and a smooth and glossy coating film will not be obtained. However, there are disadvantages in that it may not be possible to do this, or the paint may be significantly deformed due to heating during the baking process. For this reason, it is necessary to add polyethylene and/or ethylene-α-olefin copolymer to the extent that adhesion to the coating film is not impaired to improve trichloroethane steam cleaning resistance and heat resistance.

Therefore, the three types of constituents used in the present invention each play the following roles.

That is, EVA with a low vinyl acetate content forms the skeleton of the polymer composition of the present invention and plays a role in maintaining heat resistance.

EVAtf has a large vinyl acetate content, provides vinyl acetate units as polar groups that improve adhesion to the coating film, and also provides polyethylene and/or ethylene-α- as described below.
The addition of the olefin copolymer serves as a softener to offset the hardening of the polymer composition.

The polyethylene and/or the ethylene-α-olefin copolymer share the role of improving heat resistance and trichloroethane vapor cleaning resistance.

Of course, the polymer composition of the present invention can be used not only for automatic military exterior parts but also for EVA molded products that require painting, including molded products obtained by extrusion molding, injection molding, and tube molding, as well as molded products such as films and sheets. It can also be used for

In addition, the polymer composition of the present invention has improved heat resistance while maintaining the number of vinyl acetate units as polar groups, so it is effective in improving the adhesion between metal foil and molded products during hot stamping. be.

The present invention will be explained in more detail below with reference to Examples.

〔Example〕

In the following Examples and Comparative Examples, the flexural rigidity, hardness, deformation under self-weight, low-temperature flexibility, and paintability of the polymer compositions were measured by the following methods to evaluate these performances.

1. JIS using a strip-shaped sample with a bending rigidity of 20 m x 100 w + x 3
Measured in accordance with K-7106.

2. Hardness (A, D) Stack 4 strip-shaped samples of 20s++aX100■×3■ and measure the A and D hardness of JISK6301. J
Measured according to IS K7215.

3. Hold one end of a strip-shaped sample with self-weight deformation of 20 x 10 x 10 Os and keep the sample horizontal. 1. Measure the amount of sagging of the sample during heating after being left undisturbed for 3 hours while heating at a predetermined temperature. death,
The heat resistance of the polymer composition was evaluated by expressing it in units. In order to achieve the purpose of the present invention, 80°C, 9°C
It is desirable that the amount of deformation due to its own weight at 0℃ is 10.20m5+ or less, but in practical terms, methods have been developed to produce molded products by inserting metal fittings, and methods to perform baking under mild conditions with improved paints. Since it has become possible to prevent the thermal deformation of molded products to a certain extent, a maximum deformation amount under its own weight of 20.30 square meters or less was considered to be acceptable.

4. Low-temperature bending properties: Using a dematcher bending tester specified in JIS K6301, bend a sample of 20 days width x 3 haze thickness at -30°C (maximum 100cm, minimum 70cm, 300 times/m 1
n) The total number of times the sample was bent until it broke was measured.

To achieve the objectives of the present invention, low temperature flexibility (13,
000 times or more is required.

5. Adhesion to the paint film A sheet of ethylene-vinyl acetate copolymer (150 x 80 m x 2 sheets) made by injection molding was first wiped with White Garlin to degrease it, then coated with ethylene-vinyl acetate copolymer as a primer. A toluene solution (solid content: 5%) of a partially saponified product (contains vinyl acetate! 28%) was spray applied (thickness: 10 μm), dried at room temperature for 10 minutes, and then a two-component polyurethane resin paint (Dainippon Paint Co., Ltd. made by Planit Usu 160) and painted with air spray (thickness 40
μm) and dried for 10 min at room temperature and then 80°C.

It was heated for 40 minutes to force dry it.

To check the adhesion of the paint film, test the base using sellotape after one week). Please go and evaluate it.

In order to achieve the object of the present invention, it is necessary that the adhesion with the coating film be rated O for peeling in the substrate test.

Regarding the appearance of the paint film, if the surface of the molded product is significantly roughened and uneven due to the trichloroethane steam cleaning in pre-treatment, the resulting paint film will lose its luster due to diffused reflection on the surface.
Visually evaluate the gloss of the paint film.

It was displayed in three stages: OΔ×.

Example 1. ~41, Comparative Example 1. ~4° As shown in Table 1, each component was melt-blended at each composition ratio using a 40 mm extruder. The various physical properties of the composition were evaluated and shown in Table 1.

Comparative Example 1 is the evaluation result for component (4) forming the skeleton of Example 1. In this case, the vinyl acetate content of the composition is low, so the heat resistance is excellent, but the adhesion to the paint film is poor. Inferior.

Comparative Example 2 used a type of directly synthesized EVA'i having almost the same vinyl acetate content as the formulation of Example 1, but in this case the adhesion to the paint film was good.

Both the appearance and heat resistance of the coating are poor.

Comparative Example 3 is composed only of components (A) and (B),
Q.

The blend ratio of the component ω) and the vinyl acetate content of the composition were the same as in Example 1, but in this case the heat resistance was improved and the coating adhesion was good, but the coating appearance was poor.

Comparative Example 4 is composed only of (4) and (C) E components, and the vinyl acetate content t of the composition is almost the same as Example 1, but
In this case, the adhesion and appearance of the coating film are good, but the heat resistance is poor. On the other hand, Example 1 has good coating film adhesion, coating appearance, and heat resistance.

Examples 2 to 3 High-pressure low density I-lyeethylene and linear low-density I-lyeethylene were used in place of the (0 component) in Example 1, but in this case as well, the coating film was Good adhesion, paint appearance, and heat resistance.

Example 4 In Example I, the (4) component was reduced and the (B) component was increased, making it a more flexible formulation than in Example 1, but in this case as well, the coating film was Good adhesion, paint appearance, and heat resistance.

Example 5. Comparative example 5. ~9 Each component shown in Table 2 was melt-blended at each composition ratio using a 40cm extruder. The various physical properties of the composition were evaluated and shown in Table 2.

Comparative Example 5 is an evaluation result of component (A) forming the skeleton of Example 5, and in this case, heat resistance, adhesion to the coating film, and appearance of the coating were all inferior.

Comparative Example 6 is a mixture of 56 parts by weight of component (4) and 24 parts by weight of component (B) of Example 5 (vinyl acetate content 16.9%) by direct polymerization of one type of vinyl acetate content that is almost the same as that of Example 5. In this case, the obtained EVA i was used, and although the adhesion was good, both the heat resistance and the appearance of the coating were poor.

Comparative Example 7 is composed only of components (G) and (B), and contains
The blend ratio of component (B) is the same as in Example 5.

(If the composition does not contain component Q and the vinyl acetate content exceeds 15%, which is a constituent requirement of the present invention, in this case, the adhesion to the paint film is good, but the heat resistance and appearance of the paint are However, the heat resistance is significantly improved compared to Comparative Example 6, which is a case in which one type of EVA obtained by direct polymerization with the same vinyl acetate content is used.

Comparative Example 8 is the component (4) in Example 5, 561! and 24 parts by weight of component (B) to directly polymerized EVA (C
) ff component, but in this case as well, the adhesion to the coating film is good, but the heat resistance and the appearance of the coating are poor.

Comparative Example 9 consists of components (4), (B), and (C), but the composition ratio of (cJff) deviates from the structural conditions of the present invention, and in this case, the bending rigidity increases and the original This is not preferable because low-temperature flexibility, which is the excellent physical property of EVA, is impaired.

On the other hand, Example 5, which satisfies one of the constituent requirements of the present invention, has good adhesion to the coating film, heat resistance, and low-temperature flexibility.

Claims (5)

[Claims] (1) (A) 50 to 85% by weight of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 3 to 15% (B) 5 to 85% of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 25 to 45% by weight 40% by weight (C) A polymer composition comprising 5 to 25% by weight of polyethylene and/or ethylene-α-olefin copolymer, and the vinyl acetate content of the composition is 8 to 15% by weight. (2) The polymer composition according to claim 1, wherein the polyethylene and/or the ethylene-α-olefin copolymer is medium-density or high-density polyethylene with a density of 0.930 g/cm^3 or more. (3) The polymer composition according to claim 1, wherein the polyethylene and/or the ethylene-α-olefin copolymer is linear low-density polyethylene having a density of less than 0.930 g/cm^3. (4) (A) 50 to 85% by weight of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 3 to 15% (B) 5 to 85% of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 25 to 45% by weight 40% by weight (C) 5 to 25% by weight of polyethylene and/or ethylene-α-olefin copolymer, and a heat-resistant product molded from a polymer composition in which the vinyl acetate content of the composition is 8 to 15% by weight. Molded products with improved properties. (5) A molded article with improved heat resistance according to claim 4, wherein the molded article is a molded article for an automobile exterior part that can be baked and painted.