JPH0645732B2 - Polymer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field The present invention relates to polymer compositions. More specifically, it relates to an ethylene-vinyl acetate copolymer composition having improved heat resistance and coating adhesion.

(Problems to be Solved by Conventional Techniques and Inventions) Ethylene-vinyl acetate copolymers (hereinafter sometimes abbreviated as EVA) are excellent in flexibility, toughness, light weight, moldability and It has been widely used in the fields of foaming, general molding, film laminating sheet, etc. because it has the advantage that these physical properties can be adjusted to predetermined levels by changing the vinyl acetate content of the composition. For example, in the field of foaming, crosslinked high foam by a pressing method or non-crosslinked low foam by an injection molding method is used for beach sandals, slippers, women's footwear soles and the like. In general molding, EVA molded products are used in a wide variety of fields from industrial applications to daily sundries, and typical products include insulating covers for electric power, automobile interior parts, sashes, gaskets, artificial turf mats, ski shoes, and cushions. Materials and the like. Furthermore, in the field of film, laminate and sheet, EVA molded products are used in food packaging, agricultural materials and various industrial applications.

Further, since a black molded product containing carbon black is also excellent in weather resistance, it is also used as a vehicle exterior component such as a mudguard and a bumper protector.

On the other hand, in the market, competition from other materials other than EVA and further diversification of demands from customers for molded products have made it strict, and it is the current situation that improvement of physical properties of EVA is strongly desired.

For example, in order to enhance the decorativeness of the above-mentioned automobile exterior parts, which have been mainly black in the past, there is an increasing demand for applying the same color as the body of a passenger car or marking with a hot stamp.

To meet this demand, the conventional EVA has a drawback that the molded product is deformed by heating in the baking process of the coating material at 80 ° C. for 30 minutes, for example, because of insufficient heat resistance. As a countermeasure, EV with a relatively high melting point and low vinyl acetate content
When A was used, there was a drawback that the essential adhesion of the coating film was impaired, and there was no EVA that satisfied both the adhesion of the coating film and the heat resistance of the molded product.

In addition, in the coating process of polypropylene molded products, such as polypropylene bumpers, in order to remove stains such as mold release agent adhering to the surface of the molded products and obtain stable coating adhesion, pretreatment of coating Trichlorenta vapor cleaning is generally performed as a process. When this trichloroethane vapor cleaning was applied to an EVA molded product, a smooth and glossy coating film could not be obtained because the surface of the EVA molded product was rough and remarkably uneven.

For this reason, olefin-based thermoplastic elastomers and thermoplastic urethane resins, which are more expensive than EVA, are used as coating resins for exterior parts such as mudguards and bumper protectors, but EVA, which is cheaper than these resins, is used. There is a strong demand for improving the paintability of.

As a solution to this, a polymerization composition comprising EVA having a high vinyl acetate content, EVA having a low vinyl acetate content, polyethylene and / or an ethylene-α-olefin copolymer (hereinafter referred to as an ethylene-based copolymer), We have proposed a paintable ethylene-vinyl acetate copolymer composition that has both coating adhesion and heat distortion resistance (Japanese Patent Application No. 61-2520).
No. 57), this ethylene-vinyl acetate copolymer-based composition has good initial adhesion after coating but is water resistant (for example, immersed in warm water at 40 ° C. for 240 hours) or moisture resistant (for example, 5%).
In a durability test of a coating film such as 0 ° C., 95% RH (120 hours stationary), a small spot called a blister is generated due to a decrease in coating film adhesion force, and in a worse case, peeling of the coating film in a cross-cut test. The inconvenience occurred.

Therefore, it is required to stabilize the coating film adhesion of the ethylene-vinyl acetate copolymer type composition having improved heat resistance.

(Means for Solving the Problems) Then, the inventors of the present invention have conducted diligent research on a method for stabilizing coating adhesion of the ethylene-vinyl acetate copolymer-based composition, and as a result, It has been found that such a problem can be effectively solved by further blending a polymer containing a specific rubbery segment with a blend composed of two different types of EVA and a specific ethylene-based polymer.

Therefore, the present invention provides (A) an ethylene-vinyl acetate copolymer having a vinyl acetate content of 3 to 15% by weight, 50 to 85% by weight, and (B) an ethylene-vinyl acetate copolymer having a vinyl acetate content of 25 to 45% by weight.
Vinyl acetate copolymer 5 to 40% by weight, (C) polyethylene and / or ethylene-α-olefin copolymer 5 to 25% by weight, and (D) a polymer containing a rubbery segment, the above-mentioned component (A) ， (B)
And 3 to 30 parts by weight per 100 parts by weight of (C) in total, and the vinyl acetate content is in the range of 8 to 15% by weight based on the total amount of the components (A), (B) and (C). A certain polymer composition.

The EVA of the component (A) having a low vinyl acetate content used in the present invention has a vinyl acetate content of 3 to 15%, preferably 5 to 12%. Although it is related to the physical properties of (B), (C), and (D) components and the compounding ratio, in general, when the vinyl acetate content is less than 3%, the molded product becomes hard and the cold shock resistance is poor, and the coating film It also has poor adhesion with. On the other hand, the vinyl acetate content is 15%
Beyond the above, even if an attempt is made to improve the heat resistance by adding the below-mentioned (C) and (D) components, only a hard molded product can be obtained because the addition amount of the (C) and (D) components increases, and the characteristics of EVA It is difficult to improve the heat resistance while maintaining the flexibility.

The EVA of the component (B) having a high vinyl acetate content used in the present invention has a vinyl acetate content of 25 to 45%, preferably 27 to 35%. When the vinyl acetate content is less than 25%, 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, when the vinyl acetate content exceeds 45%, the moldability is poor and, for example, the adhesion to the mold during injection molding becomes strong, and when the mold releasability deteriorates or is remarkable, the molded product itself becomes sticky. It happens.

The component (C) polyethylene and / or ethylene-α-olefin copolymer used in the present invention is an ethylene homopolymer or a copolymerizable ethylene with propylene, butene, heptene, 4-methyl-pentene-1, octene, etc. It is a copolymer with an α-olefin having 3 to 8 carbon atoms.

Component (C) does not extremely impair the balance between heat resistance and flexibility obtained by the combination of both components (A) and (B), and is a molded product when subjected to trichloroethane vapor treatment as a pretreatment for coating. It is necessary that the ethylene homopolymer or copolymer does not cause remarkable unevenness on the surface and gives a smooth and glossy appearance after coating. Specifically, it is high density, medium density, low density polyethylene, linear low density polyethylene or the like. Among these polymers, high-density, medium-density and linear low-density polyethylene are preferable from the viewpoint of improving the heat resistance of the molded product, but a polymer having a density of 0.930 g / cm ³ or more is most preferable.

The mixing ratio of the components (A), (B) and (C) is 50 to 85 for the component (A).
% By weight, 5-40% by weight of component (B), 5-25% by weight of component (C), and the vinyl acetate content of the composition is 8-15% by weight. Further, the polymer composition of the present invention is extrusion molded, injection molded,
Since it is molded by compression molding or the like, its melt flow rate (hereinafter abbreviated as MFR) is preferably in the range of 0.1 to 100.

Further, if the vinyl acetate content of the composition is less than 8%, the adhesion of the coating film is poor, the molded product is hard and the cold bending resistance is poor. on the other hand,
If the vinyl acetate content exceeds 15%, the heat resistance is poor.

The polymer (D) containing a rubbery segment used in the present invention is not completely and uniformly dispersed when an ethylene-vinyl acetate copolymer-based resin composition is blended with a composition containing this rubbery segment, As a result, if the surface of the molded product obtained by injection molding or extrusion molding has moderate irregularities and the surface becomes matt in appearance, the irregularities improve the adhesion of the coating film due to the anchoring effect of the coating film. It is a polymer containing such a rubbery segment.

The polymer containing the rubber segment means not only a so-called rubber polymer in which the polymer chain is composed of the rubber segment alone, but also an elastomer copolymer in which a rubber segment is incorporated in a part of the polymer chain in the form of copolymerization. A polymer, a modified polymer, or a polymer in which the rubber polymer, the elastomer copolymer, or the like is blended is included.

Examples include styrene-butadiene rubber, polybutadiene rubber, and ethylene-propylene-diene terpolymer, high-impact polystyrene containing styrene-butadiene rubber as the rubber substance, ABS containing polybutadiene rubber or styrene-butadiene rubber as the rubber substance. Resins and olefin-based thermoplastic elastomers containing an ethylene-propylene-diene terpolymer as a rubber substance are available.

Among these polymers, a polyolefin-based thermoplastic elastomer obtained as a pelletized product is preferable because it is flexible and easy to handle. An example of such a polyolefin-based thermoplastic elastomer is Mirastomer (Mitsui Petrochemicals).

The ethylene-vinyl acetate polymers (A), (B) and (C) and the rubber segment-containing polymer (D) are blended in proportions of ethylene-vinyl acetate copolymers (A), (B) and (C). ) 30 to 3 parts by weight of the polymer (D) containing a rubber segment with respect to 100 parts by weight.

When the compounding ratio of the polymer containing the rubbery segment exceeds 30 parts by weight, the degree of roughening of the skin is so large that the appearance of the coated film is impaired. On the other hand, when the amount is less than 3 parts by weight, the degree of surface roughening is small and the effect of improving the coating film adhesion may be insufficient.

The polymer composition of the present invention includes a filler such as clay, talc, calcium carbonate, silica or a partially coated product in which a part of the skin of the molded product directly appears on the surface to the extent that the performance of the polymer composition is not impaired. In some cases colorants such as carbon black,
Titanium oxide, organic pigments, known antioxidants, weathering stabilizers and the like can be added.

Two types of EVA are used to prepare the polymer composition of the present invention.
And polyethylene and / or ethylene-α-olefin copolymer and a polymer containing a rubbery segment are simultaneously or successively dry-blended or melt-blended. The dry blend is mixed using various blenders such as a Hensiel mixer, a tumbler mixer, and a ribbon blender. In the case of melt blending, mixing may be performed using a single-screw extruder, a twin-screw extruder, a Banbury mixer, etc. and there is no particular limitation.

Using the polymer composition thus obtained, by thermoforming such as known extrusion molding method, injection molding method, compression molding method and the like, not only automobile exterior parts such as mudguards and bumper protectors but also the above-mentioned each It is possible to mold a molded product.

The steps of coating a molded article using the composition of the present invention as a raw material will be described below to further clarify the embodiment of the present invention.

That is, in order to coat the 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 the molded article, an organic solvent such as white gasoline or alcohol. Although there is a method of wiping the surface of the molded product with, there is trichloroethane vapor cleaning as a method suitable for a mass production process and a method of obtaining a more stable coating film adhesive force. What is this trichloroethane vapor cleaning? Soak the molded product in the vapor of trichloroethane and drop the droplets of trichloroethane condensed on the surface of the cold molded product to the surface of the molded product to remove the stains on the surface of the molded product. At the same time, it is a method of appropriately roughening the surface of the molded article to obtain good coating film adhesion. If necessary, as a primer for coating EVA molded products, for example, a solution mainly composed of a chlorinated polyolefin or a partially saponified ethylene-vinyl acetate resin may be uniformly spray-coated with a dipping or spray gun. The molded article is immersed in the alcoholic alkaline solution described in JP-A-54-125268 to surface-treat the EVA molded article.

A typical example of the paint used for coating EVA is a two-component polyol-curable polyurethane paint generally composed of polyisocyanate and polyol.

The polyol component is a polyester polyol composed of an organic acid such as phthalic acid or adipic acid and a diol such as ethylene glycol or propylene glycol, poly (oxypropylene ether) polyol, poly (oxyethylene-
There are polyether polyols such as propylene ether) polyols and acrylic polyols that are derivatives of acrylic acid.

As a polyisocyanate, Desmodur IL (Bayer
Company products) and Desmodur Aromatic polyisocyanates such as L
Card or coronate HL (product of Nippon Polyurethane Company) and De
smodur If an aliphatic polyisocyanate such as N is used
Be done.

In order to produce a flexible and weather resistant polyurethane coating for EVA coating, polyester polyol or acrylic polyol is used as the polyol component, and non-yellowing aliphatic polyisocyanate is used as the polyisocyanate component. preferable.

Other additives such as amines and organic metal salts as catalysts, oil-soluble dyes and pigments as colorants, moisture stabilizers and flow improvers, and aromatic hydrocarbons, esters, or It is made a paint using ketones.

The polyurethane paint may be applied by using a brush coater, a roll coater or the like, but in general, spray coating with a spray gun is performed.

The baking of the polyurethane coating applied to EVA is generally performed by heating at 70 ° C. to 80 ° C. for 30 minutes to 1 hour.

(Operation) The polymer composition of the present invention comprises two types of EVA having different vinyl acetate contents, a specific polyethylene and / or an ethylene-α-olefin copolymer, and a polymer further containing a rubbery segment. A molded article made from this composition is a single component E produced by direct polymerization.
It has excellent physical properties that cannot be obtained with VA, especially heat resistance and coating film adhesion. This effect will be explained by taking the coatability of the molded product as an example. The EVA molded product using the composition of the present invention as a raw material does not cause remarkable unevenness on its surface during trichloroethane cleaning and does not impair its appearance. It is possible to prevent the coating film from being deformed by heating in the baking process while maintaining the adhesion to the coating film.

That is, the composition of the present invention is an EV having a low vinyl acetate content.
Two types of EVA, A and EVA with a high vinyl acetate content
However, the EVA compound thus obtained is significantly improved in heat distortion resistance as compared with the single-component EVA obtained by direct polymerization, and its self-weight deformation amount is very small. At the same time, it is characterized in that it contains a polymer having a sufficient amount of a vinyl acetate unit which is a polar group necessary for obtaining good adhesion to a coating film.

However, even with the two types of EVA compounds thus obtained, when trichloroethane cleaning is applied as a pretreatment for coating, the surface of the molded product is significantly roughened to obtain a smooth and glossy coating film. However, there are drawbacks such as not being able to do so and the deformation caused by heating in the baking process of the paint becomes large. Therefore, polyethylene and / or ethylene-α-olefin copolymer is added to the extent that the adhesion with the coating film is not impaired, and trichloroethane vapor cleaning resistance and heat resistance are improved,
Further, a polymer containing a rubbery segment is added to roughen the surface of the molded article to an appropriate degree, and the anchoring effect of the coating film improves the durability of the coating film adhesion.

Therefore, each of the four kinds of constituent components used in the present invention has the following roles.

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

EVA having a high vinyl acetate content provides a polymer composition by providing a vinyl acetate unit as a polar group for improving adhesion with a coating film and adding a polyethylene and / or an ethylene-α-olefin copolymer described later. Plays a role of softening to offset the hardening of the.

The polyethylene and / or ethylene-α-olefin copolymer has a role of improving heat resistance and trichloroethane vapor scrubbing resistance.

The polymer containing a rubbery segment is one in which the surface of the molded article is appropriately roughened and the durability of the coating film adhesion is improved by the anchoring effect of the coating film.

Needless to say, the polymer composition of the present invention requires coating of molded articles including films, sheets, etc. other than molded articles obtained by extrusion molding, injection molding, injection molding or blow molding, in addition to exterior parts for automobiles. It can also be used for EVA molded products.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Examples) In the following Examples and Comparative Examples, the flexural rigidity, hardness, amount of self-weight deformation, low temperature flexibility, and coatability of the polymer composition were measured by the following methods, and the performances thereof were evaluated. .

1. JIS using flexural rigidity 20 mm x 100 mm x 3 mm short shelf sample
It was measured according to K-7106.

2. Hardness (A, D) Four short-shelf-shaped samples of 20 mm x 100 mm x 3 mm are stacked and the A and D hardnesses are JISK-6301 and JI, respectively.
It was measured according to SK-7215.

3. Deformation amount of self-weight 20mm x 100mm x 3mm Short shelf-shaped sample One end of the sample is held and the sample is kept horizontal. , Mm
The heat resistance of the polymer composition was evaluated by displaying in units. In order to achieve the object of the present invention, 80 ° C., 90
It is desirable that the amount of self-weight deformation at ℃ is less than 10 and 20 mm respectively, but practically, a method of inserting metal fittings to produce a molded product and a method of improving baking and baking under mild conditions have been developed. Since it has become possible to prevent thermal deformation of molded products to some extent, the maximum self-weight deformation amounts of 20 and 30 mm or less, respectively, are regarded as acceptable.

4. Adhesion of coating film An ethylene-vinyl acetate copolymer sheet (150 mm x 80 mm x 2 mm) prepared by injection molding is first wiped with white gasoline to degrease it, and then an ethylene-vinyl acetate copolymer (vinyl acetate) is used as a primer. A toluene solution (solid content: 5%) of a partially saponified product having a content of 28%) is spray-coated (thickness: 10 μm) and dried at room temperature for 10 minutes, and then a two-component polyurethane resin coating (manufactured by Dainippon Paint, Prenit u # 160) painted with air spray (thickness 40
μm), dried at room temperature for 10 minutes, and then heated at 80 ° C. for 40 minutes to forcibly dry.

The adhesiveness of the coating film was evaluated by performing a cross-cut test using cellophane tape one day later (initial test).

In the water resistance test, the coated product obtained in this way
The film was immersed in warm water of 0 ° C. for 240 hours and subjected to a water resistance test of the coating film. In order to achieve the object of the present invention, it is necessary that the adhesion to the coating film is 10 or less per 100 peels in the cross cut test (water resistance test).

Regarding the appearance of the coating film, if the surface of the molded product of trichloroethane vapor cleaning as the pretreatment is significantly roughened and irregularities are generated, the obtained coating film loses its gloss due to the irregular reflection of the surface. Was visually evaluated and displayed in three grades of ◯ Δ ×.

Example 1. EVA with a low vinyl acetate content (vinyl acetate content 10
%, MFR 20 dg / min) EVA with a large vinyl acetate content in 56 parts by weight (vinyl acetate content 33%, MFR 30 dg
/ Min) High-density polyethylene (Mitsui Petrochemicals HiZex 2200J Density 0.965g /
cm ³ , MFR 13 dg / min) 20 parts by weight and olefinic thermoplastic elastomer (Mitsui Petrochemical product Mirastomer 5030B, density 0.88 g / cm ³ , MFR 0.2 dg
/ Min) was melt-blended using a 40 mm extruder, and various physical properties of the polymer composition were evaluated and shown in Table 1.

Comparative Example 1. A polymer composition was prepared by removing the olefinic thermoplastic elastomer from the polymer composition of Example 1 and evaluated for its physical properties. The results are shown in Table 1.

Comparative example 2. A polymer composition was prepared by removing high density polyethylene from the polymer composition of Example 1 and evaluated for various physical properties. The results are shown in Table 1.

As a result, in Example 1, both the appearance of the coating and the adhesion of the coating film were good, but in Comparative Example 1 containing no olefinic thermoplastic elastomer, the water resistance of the coating film was poor, and the high density polyethylene was also used. In Comparative Example 2 which did not contain, the heat resistance was poor and the appearance of the coating was poor.

Examples 2-3. Among the polymer compositions of Example 1, instead of the olefinic thermoplastic elastomer, a polymer composition containing a rubber segment-containing polymer shown in Table 1 was prepared, and various physical properties were evaluated. The results are shown in Table 1.

Comparative Examples 3-4. Polymer compositions were prepared by removing the high density polyethylene of the polymer compositions of Examples 2 to 3 and evaluated for various physical properties. The results are shown in Table 1.

As a result, in Examples 2 to 3, the appearance of the coating and the adhesion of the coating film were good, but in Comparative Examples 2 to 3 containing no high-density polyethylene, the appearance of the coating was poor.

Examples 4-6. EVA with a low vinyl acetate content (vinyl acetate content 6%,
MFR18dg / min) 70 parts by weight, EVA with a high vinyl acetate content (33% vinyl acetate, MFR30dg / mi)
n) 20 parts by weight of medium density polyethylene (Mitsui Petrochemical Neozex 45150, density 0.944 g / cm
³ , MFR 16 dg / min) 10 parts by weight and olefinic plastic elastomer (Mitsui Petrochemicals Mirastomer 9070B density 0.89 g / cm ³ , MFR 20 dg / mi
n) The physical properties of the polymer composition prepared in the same manner as in Example 1 were evaluated using the predetermined amounts shown in Table 2. The results are shown in Table 2.

Comparative Example 5. Among the polymer compositions of Example 5, a polymer composition excluding the olefinic thermoplastic elastomer was prepared and various physical properties were evaluated. The results are shown in Table 2.

Comparative Example 6. Among the polymer compositions of Example 5, a polymer composition excluding the medium density polyethylene was prepared and various physical properties were evaluated. The results are shown in Table 2.

Examples 7-9. In the polymer compositions of Examples 4 to 6, linear low-density polyethylene was used instead of medium-density polyethylene (Mitsui Petrochemical Ultzex 20200J density 0.920 g / c).
m ³ and MFR 20 dg / min) were mixed to prepare a polymer composition, and various physical properties were evaluated. The results are shown in Table 3.

Comparative Example 7. In Example 8, a polymer composition excluding the olefinic thermoplastic elastomer was prepared and various physical properties were evaluated. The results are shown in Table 3.

As a result, in Examples 4 to 9, the appearance of the coating was good, and the adhesion of the coating film was better as the blending amount of the olefinic thermoplastic elastomer increased.

On the other hand, in Comparative Example 6 containing no polyethylene component, the heat resistance was poor and the appearance of the coating was poor. On the other hand, in Comparative Examples 5 and 7 containing no olefinic thermoplastic elastomer, the water resistance of the coating film was poor.

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Claims (3)

[Claims] 1. An ethylene-vinyl acetate copolymer having a vinyl acetate content of 3 to 15% by weight (A) 50 to 85% by weight (B) an ethylene acetate having a vinyl acetate content of 25 to 45% by weight
Vinyl acetate copolymer 5 to 40% by weight (C) polyethylene and / or ethylene-α-olefin copolymer 5 to 25% by weight and (D) a polymer containing a rubber segment, (A) and (B) above as well as
It is composed of 3 to 30 parts by weight per 100 parts by weight of (C), and has a vinyl acetate content of 8 to 15% by weight based on the total amount of the components (A), (B) and (C). Combined composition. 2. Polyethylene and / or ethylene-α
Polymer composition according to claim 1, wherein the olefin copolymer is a medium or high density polyethylene having a density of 0.930 g / cm ³ or more. 3. Polyethylene and / or ethylene-α
Polymer composition according to claim 1, wherein the olefin copolymer is a linear low density polyethylene having a density of less than 0.930 g / cm ³ .