JPH064731B2 - Polymer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polymer composition. More specifically, it relates to an ethylene-vinyl acetate copolymer composition having improved heat resistance.

[Problems to be Solved by Prior Art and Invention]

Ethylene-vinyl acetate copolymer (hereinafter sometimes abbreviated as EVA) is excellent in flexibility, toughness, light weight, moldability and by changing the vinyl acetate content in the copolymer,
Since it has the advantage that these physical properties can be adjusted to desired levels, it has been widely used in the fields of foaming, general molding, film laminating sheet and the like. 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, sash gaskets, artificial grass mats, ski shoes, cushioning materials. Etc. Furthermore, EV in the film, laminating and sheet fields
A 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 with other materials other than EVA, and demands from customers for molded products have become diversified and stricter.
At present, it is strongly desired to improve the physical properties of A.

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.

In response to this demand, the conventional EVA has a drawback that the molded product is deformed by heating in the paint baking step at 80 ° C. for 30 minutes because of insufficient heat resistance. As a countermeasure, EVA with a relatively high melting point and low vinyl acetate content
However, there was no EVA that satisfied both the adhesiveness 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 Trichloroethane steam cleaning is generally performed as a process. When this trichloroethane vapor cleaning was applied to an EVA molded product, the surface of the EVA molded product was roughened, resulting in remarkable unevenness, so that a smooth and glossy coating film could not be obtained.

Therefore, 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 is cheaper than these resins. There is a strong demand for improving the paintability of.

Also, in the same way as painting, the hot stamp that heats the molded product to semi-melt the surface and then momentarily applies pressure to the metal foil to transfer it, in order to improve the adhesion with the metal foil, transfer with a larger pressure. There is a demand for EVA that does not undergo thermal deformation.

[Means for solving problems]

The present inventor, as a result of earnest research on a method of improving physical properties, particularly heat resistance, which has been a drawback of conventional EVA molded products,
It has been found that such a problem can be effectively solved by using as a raw material a polymer composition composed of two specific types of EVA having different vinyl acetate contents and a specific ethylene polymer.

Accordingly, the present invention provides (A) an ethylene-vinyl acetate copolymer having a vinyl acetate content of 3 to 11% by weight, 50 to 85% by weight, and (B) an ethylene-vinyl acetate copolymer having a vinyl acetate content of 25 to 35% by weight. Polymer composition comprising 5 to 40% by weight of the polymer and (C) 5 to 25% by weight of polyethylene and / or ethylene-α-olefin copolymer, wherein the vinyl acetate content of the composition is 8 to 15% by weight. Is.

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 11%, preferably 5 to 10%. Although it is related to the physical properties and blending ratio of components (B) and (C), 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 adhesion to the coating film is also low. Is also inferior. On the other hand, when the vinyl acetate content exceeds 11%, even if an attempt is made to improve the heat resistance by adding the component (C) described later, only a hard molded product can be obtained because the amount of the component (C) added increases, and It is difficult to improve heat resistance while maintaining the characteristic flexibility.

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

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

The component (C) does not extremely impair the heat resistance obtained by the combination of both components (A) and (B), and the surface of the molded product undergoes trichlorethane vapor treatment as a pretreatment for coating. It is necessary that the ethylene homopolymer or copolymer gives a smooth and glossy appearance after coating without causing remarkable unevenness. Specifically, they are high density, medium density, low density polyethylene, linear low density polyethylene, and the like. Among these polymers, high-density, medium-density and linear low-density polyethylenes are preferable from the viewpoint of improving the heat resistance of molded articles, but polymers having a density of 0.930 g / cm ³ or more are 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 western part (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.

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

In the case of a partially coated article in which the polymer composition of the present invention is a filler such as clay, talc, calcium carbonate, silica or a part of the skin of the molded article is a straight surface so long as the performance of the polymer composition is not impaired. A colorant, for example, carbon black, titanium oxide, an organic pigment, a known antioxidant, a weathering stabilizer, or the like can be added to the above.

The polymer composition of the present invention is prepared by dry-blending or melt-blending two kinds of EVA and polyethylene and / or ethylene-α-olefin copolymer simultaneously or sequentially. The dry blend is mixed using various blenders such as a Henschel 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 bumper 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, etc. as well as automobile exterior parts such as mudguard bumper protectors It is possible to mold the 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, pretreatment is first performed. As a small-scale method for cleaning the surface of the molded product with fat, there is a method of wiping the surface of the molded product with an organic solvent such as white gasoline or alcohol, which is suitable for mass production processes and has a more stable coating. As a method of obtaining the film adhesive force, there is trichloroethane vapor cleaning. 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 containing a chlorinated polyolefin or a partially saponified ethylene-vinyl acetate resin as a main component can be uniformly spray-coated with a dipping or spray gun, or The molded article is surface-treated by immersing the molded article in the alcoholic alkaline solution described in JP-A-54-125268.

A typical example of the coating material used for coating EVA is a two-component polyol effect type polyurethane coating material composed of polyisocyanate and polyol.

The polyol component is a polyester polyol consisting 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.

Polyester polyols and acrylic polyols are used as the polyol component, and non-yellowing aliphatic polyisocyanate is used as the polyisocyanate component to make flexible and weather-resistant polyurethane coatings for EVA coating. Is preferred.

In addition, amines and organic metal salts as catalysts, oil-soluble paints and pigments as colorants, additives such as water stabilizers and flow improvers are compounded, 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 paint applied to EVA is generally performed by heating at 70 ° C to 80 ° C for 30 minutes to 1 hour.

[Action]

The polymer composition of the present invention comprises two specific types of EVA having different vinyl acetate contents and a specific polyethylene and / or ethylene-α-olefin copolymer. A molded article using this composition as a raw material has excellent physical properties, especially heat resistance, which cannot be obtained by a single-component EVA produced by direct polymerization. Explaining this effect by taking the paintability of a molded product as an example, an EVA molded product using the composition of the present invention as a raw material has remarkable irregularities on its surface during trichloroethane cleaning,
It is possible to prevent deformation of the coating film due to heating in the baking process while maintaining the adhesiveness with the coating film without impairing its appearance.

That is, the composition of the present invention is an EVA having a low vinyl acetate content.
And EVA with high vinyl acetate content are blended, but the EVA blend thus obtained has a higher heat distortion resistance than the single component EVA obtained by direct polymerization. It contains a polymer that is significantly improved and has a very small self-weight deformation amount, and also has sufficient vinyl acetate units, which are polar groups necessary for obtaining good adhesion to the coating film. It has the characteristics of

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 and a smooth and glossy coating film can be obtained. There is a drawback that it cannot be done or the deformation due to heating in the baking process of the paint becomes large. Therefore, polyethylene and / or
Or by adding ethylene-α-olefin copolymer,
It has improved trichloroethane vapor cleaning resistance and heat resistance.

Therefore, the three kinds of constituent components used in the present invention have 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 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.

Of course, the polymer composition of the present invention is an EVA molded product that requires coating of a molded product obtained by extrusion molding, injection molding or blow molding as well as a molded product including a film or a sheet in addition to exterior parts for automobiles. Can also be used for

Further, since the polymer composition of the present invention has improved heat resistance while maintaining the number of vinyl acetate units as polar groups, it is also effective in improving the adhesion of the metal foil and the molded product even in hot stamping. is there.

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

〔Example〕

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 these performances were evaluated.

1. Flexural rigidity 20mm x 100mm x 3mm using strip sample JISK-
7106 was measured.

2. Hardness (A, D) Four strip-shaped samples of 20 mm x 100 mm x 3 mm are stacked and the A and D hardnesses are JIS K6301 and JIS K7, respectively.
215 according to the measurement.

3. Deformation amount of self-weight 20mm x 100mm x 3mm One end of a strip-shaped sample is held and the sample is kept horizontal and left standing in a heating oven at a predetermined temperature for 3 hours to measure the amount of sagging of the sample during heating, 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 ° C be 10 or 20 mm or less, but in practice, a method of inserting metal fittings to produce a molded product, a method of improving paint and baking under mild conditions, etc. have been developed. Since it has become possible to prevent the thermal deformation of the molded product to some extent, the maximum self-weight deformation amounts of 20 mm and 30 mm or less, respectively, were accepted.

4. Low temperature bending property Using a Dematcher bending tester specified in JIS K6301, a 20 mm wide x 3 mm thick sample is bent at -30 ° C (maximum 100 mm, minimum 70 mm, 300 times / min) until the sample breaks. The number of times of bending was measured. In order to achieve the object of the present invention, it is necessary that the low temperature flexibility is 3,000 times or more.

5. Adhesion with coating film An ethylene-vinyl acetate copolymer sheet (150 mm x 80 mm x 2 mm) made by injection molding was first wiped with white gasoline to degrease it, and then used as a primer for ethylene-vinyl acetate copolymer (vinyl acetate 28%) of a partially saponified toluene solution (solid content: 5%) is applied by spraying (thickness: 10 μm) and dried at room temperature for 10 minutes, and then a two-pack type polyurethane resin coating (Dainippon Paint, Planit u160 ) With air spray (thickness 40μ
m), dried at room temperature for 10 minutes, and then heated at 80 ° C. for 40 minutes forcibly dried.

The adhesiveness of the coating film was evaluated after one week by performing a cross-cut test using cellophane tape. In order to achieve the object of the present invention, it is necessary that the adhesion to the coating film is 0 when peeled in a cross cut test.

Regarding the appearance of the coating film, when the surface of the molded product is significantly roughened by the pretreatment with trichloroethane vapor cleaning and irregularities are generated, the obtained coating film loses gloss due to irregular reflection on the surface.
The gloss of the coating film was visually evaluated and displayed in three grades of ◯ Δ ×.

Examples 1 to 6 The components shown in Table 1 were melt-blended with each constituent ratio using a 40 mm extruder. Various physical properties of the composition were evaluated and shown in Table 1. In Examples 1, 2, and 3, 70 parts by weight of EVA containing 6% by weight of vinyl acetate was used as the component (A), and 20 parts by weight of EVA containing 33% by weight of vinyl acetate was used as the component (B). In the case of Example 1, medium density polyethylene,
In the case of Example 2, high-pressure low-density polyethylene was blended, and in the case of Example 3, linear low-density polyethylene was blended in an amount of 10 parts by weight each. It can be seen from the evaluation results in Table 1 that all the compositions are excellent in the adhesion of the coating film, the appearance of the coating, and the heat resistance.

Example 4 is a composition in which the component (A) is reduced and the component (B) is increased in Example 1, which is a composition having a softer composition than that of Example 1. In this case as well, Similarly, the coating film adhesion, coating appearance, and heat resistance are all good.

In Example 5, 56 parts by weight of EVA having a vinyl acetate content of 10% by weight as the component (A) and vinyl acetate content 3 as the component (B) were used.
A composition having a slightly higher amount of the component (C) than the compositions of Examples 1 to 4 in which 24 parts by weight of 3% by weight of EVA and 20 parts by weight of high-density polyethylene as the component (C) are combined. Although the composition is slightly harder than those of Nos. 2 to 4, the coating film adhesion, coating appearance, and heat resistance are all good.

In Example 6, the component (B) of Example 1 was used containing 28% by weight of vinyl.
Although it is a composition replaced with EVA,
Excellent coating appearance and heat resistance.

Comparative Examples 1 to 14 The components shown in Table 2 were melt-blended in each constituent ratio using a 40 mm extruder.

Various physical properties of the composition were evaluated and are shown in Table 2.

Comparative Examples 1 to 4 are EVs having different vinyl acetate contents.
Although only A was used alone, it can be seen that the appearance of the coating was inferior in any case.

Of these, Comparative Example 1 forms the skeleton of Example 1 (A)
Although it corresponds to the component, in this case, since the vinyl acetate content of the resin is small, the heat resistance is good, but the coating film adhesion is poor. Comparative Example 2 forms the skeleton of Example 5.
Although it corresponds to the component (A), it has insufficient heat resistance and coating adhesion.

Comparative Example 3 is EVA having a vinyl acetate content of 12% by weight, and Comparative Example 4 is EVA having a vinyl acetate content of 17% by weight, but both have poor heat resistance.

Comparative Examples 5 and 6 are compositions only of EVA blends in which EVA having a low vinyl acetate content and EVA having a high vinyl content are combined and blended, but neither of them improves the appearance performance of coating.

In particular, the composition of Comparative Example 6 in which the composition has a high content of hynyl acetate of 17% by weight, has insufficient heat resistance.

Comparative Examples 7, 8 and 9 are compositions in which one type of EVA and various types of polyethylene ((C) component) are combined and blended. Of these, 85 parts by weight of a vinyl acetate content of 10% by weight are included. The composition of Comparative Example 7, which was obtained by blending 15 parts by weight of linear low-density polyethylene with a vinyl acetate content as low as 85% by weight, had a good coating appearance but poor coating adhesion.

Also, the composition of Comparative Example 8 in which 90 parts by weight of EVA having a vinyl acetate content of 12% by weight and 10 parts by weight of medium density polyethylene were mixed had good appearance and adhesion of coating, but the heat distortion resistance was not sufficient.

Also, 80 parts by weight of EVA having a slightly high vinyl acetate content of 17% by weight is used, and 2 parts of high density polyethylene are used.
The composition of Comparative Example 9 in which 0 parts by weight was blended and blended did not improve the appearance of the coating, and only a composition having remarkably poor heat resistance was obtained.

Comparative Examples 10 to 12 are compositions in which two types of EVA having different vinyl acetate contents are combined, and various polyethylenes which are the component (C) are blended and blended therein, and Comparative Examples 10 and 11 are This is a composition in which the component (B) of Example 5 (vinyl acetate content 33%) is replaced with the same amount (24 parts by weight) of EVA having a vinyl acetate content of 19% by weight, which has a relatively low vinyl acetate content. The composition is a combination of EVA members.

On the other hand, Comparative Example 12 is a composition in which 20 parts by weight of 80 parts by weight of EVA having a vinyl acetate content of 17% by weight in Comparative Example 9 is replaced with EVA having a high vinyl acetate content of 33% by weight, which is relatively high. EVA with high vinyl acetate content
It is a composition in which both are combined.

From the evaluation results in Table 2, it can be seen that the compositions of Comparative Examples 10 and 11 have good coating appearance, but are inferior in the adhesion of the coating film. The composition of Comparative Example 10 also has a defect that the flexibility at low temperature is not sufficient and the flexural rigidity is slightly too high, that is, too hard.

The composition of Comparative Example 12 in which EVA having a high vinyl acetate content was combined was not good in the appearance of coating, and was significantly inferior in heat resistance.

Comparative Examples 13 and 14 are EVA having a low vinyl acetate content (component (A)) and EVA having a high vinyl acetate content defined in the present invention.
This is a composition obtained by combining and blending (Component (B)) and high-density polyethylene (Component (C)), but the blending amount of each component is outside the range specified in the present invention.

The composition of Comparative Example 13 was EVA with a low vinyl acetate content.
The amount of EVA is high, and conversely, the amount of EVA having a high vinyl acetate content is high, and the vinyl acetate content of the composition after blending is as high as 17% by weight.

From the evaluation results in Table 2, it can be seen that such a composition has significantly poor heat resistance.

In the composition of Comparative Example 14, the content of the component (C) was more than the amount specified in the present invention, and in this case, the bending rigidity was large, and the low temperature flexibility which was originally excellent physical property of EVA. Is damaged.

On the other hand, Examples 1 to 6 satisfying the constituent requirements of the present invention
Shows good properties in terms of adhesion to coating film, heat resistance, coating appearance, and low-temperature flexibility.

Claims (3)

[Claims] 1. An ethylene-vinyl acetate copolymer (A) having a vinyl acetate content of 3 to 11% by weight and an ethylene-vinyl acetate copolymer having a vinyl acetate content of 25 to 35% by weight (B).
5 to 40% by weight of vinyl acetate copolymer, 5 to 25% by weight of (C) polyethylene and / or ethylene-α-olefin copolymer, and the vinyl acetate content of the composition is 8 to 15% by weight. Polymer composition. 2. Polyethylene and / or ethylene-α
-The 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 with a density of less than 0.930 g / cm ³ .