JPH0680839A - Wheel cover - Google Patents

Abstract

PURPOSE:To provide a wheel cover giving a low protuberance at its welded part, excellent in its appearance and quality, and further excellent in its mechanical properties such as impact strength and flexural modulus of elasticity. CONSTITUTION:The wheel cover comprises (A) polypropylene resin, (B) 20wt.% of thermoplastic resin-coated glass fibers, and (C) glass fibers, the total amount of the synthetic resin components in (A) and (B) being 65-95wt.%, the total amount of the glass fibers in (B) and (C) being 5-35wt.%, and the melt-flow rate M (g/10min) of the polypropylene resin as (A) and the total amount G of the glass fibers satisfying the relation of an inequality: M<1000/G.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel cover excellent in appearance quality and mechanical properties.

[0002]

2. Description of the Related Art A wheel cover is attached to a wheel of an automobile. This wheel cover is used for the purpose of protecting the tightening bolts on the wheel and improving the design of the wheel and the automobile. By the way, in recent years, it has been considered to use a glass fiber reinforced polypropylene resin composition (hereinafter, also referred to as reinforced PPG) as a material for the wheel cover (Actual Kaihei No. 1-62333,
JP-A-3-137150). Because the strengthened PP
This is because G is generally excellent in mechanical strength, rigidity, heat resistance, and low in cost. However, the biggest problem when using the reinforced PPG is that the quality of the appearance of the wheel cover surface is inferior because it contains glass fibers.

In order to improve the surface appearance of the reinforced PPG, a method of adding an inorganic substance such as barium sulfate, calcium carbonate or talc (Japanese Patent Publication No. 1-232856).
Gazette), diameter of glass fiber and optimization of glass fiber surface treatment agent (JP-B-4-12297), addition of fibrous calcium silicate (JP-B-63-67498), ethylene-α-olefin rubber Addition (6
3-67499), optimization of glass fiber diameter, glass fiber sizing agent, and pigment component (Japanese Patent Publication No. 64-665).
No. 8, No. 64-7618, No. 64-9340).
Etc. have been proposed. All of these conventional methods are to prevent the glass fibers from floating on the wheel cover surface, improve the surface gloss, and prevent silver streaks (silver-like lines due to the glass fibers). Have.

[0004]

However, even when the conventional reinforced polypropylene resin composition is used, there is a problem with the rise in the weld portion of the wheel cover. That is, the wheel cover is often manufactured by injection molding. At that time, a plurality of resin flows occur in the cavity of the mold, and as shown in FIG. 4, the wheel cover 9 finally has a weld portion 93 at a portion where the resin flow 90 meets.

What is important here is the weld portion 93.
However, as shown in FIG. 5, a ridge 8 is formed. In FIG. 4, reference numeral 91 is a gate position at the time of molding, and 96 is a wind hole (heat dissipation hole) of the wheel cover. Reference numeral 82 in FIG. 5 indicates glass fiber. The rise 8 is formed particularly high when using a reinforced polypropylene resin composition containing glass fiber, and because of its height,
The surface appearance of the wheel cover 9 is impaired. The rise height L reaches 40 to 100 μm when the conventional PPG is used.

In particular, in the wheel cover, from the viewpoint of design improvement in recent years, the position and shape of the air holes are complicated,
Various shapes such as large holes are required, and the surface appearance at the weld is also receiving much attention. From the standpoint of surface appearance, it is necessary to suppress the height of rise to 35 μm or less. Further, it is preferably 30 μm or less.

In order to reduce the rise height, a method of strengthening the kneading degree to shorten the glass fiber length as much as possible in the PPG material manufacturing process (generally, the average length is 300 μm or less), A method of reducing the amount of glass fiber added is known. However, these methods have a problem that mechanical properties such as impact strength and flexural modulus are simultaneously reduced as the rise height of the weld is reduced. In view of the above conventional problems, the present invention aims to provide a wheel cover having a low rise height of a weld portion and excellent appearance quality and mechanical properties.

[0008]

The present invention is a wheel cover mounted on a wheel of an automobile, the wheel cover comprising:
(A) a polypropylene resin, (B) a resin-coated glass fiber previously coated with 20% (weight ratio, the same applies hereinafter) or more of a thermoplastic resin, and (C) a glass fiber. The total amount of the synthetic resin components in the component B) is 65 to 95%, and the above (B) and (C)
The total amount G of glass fibers in the components is 5 to 35%, and the melt flow rate M (g / 10 minutes) of the polypropylene resin of the component (A) and the total amount G (% by weight) of the glass fibers are , M <1000 / G, which is molded by a glass fiber reinforced polypropylene resin composition.

In the present invention, the polypropylene resin is modified with a crystalline polypropylene resin, a crystalline ethylene-propylene copolymer, or an unsaturated organic acid such as acrylic acid, maleic acid, itaconic acid, maleic anhydride or a derivative thereof. Crystalline propylene polymers, and mixtures thereof. Among these, a particularly preferable combination is a combination of a crystalline ethylene / propylene block copolymer and a modified polypropylene polymer. The crystalline ethylene / propylene block copolymer has an ethylene content of 3 to 12 wt% in terms of the balance of impact resistance, rigidity and strength.
% Is preferably contained.

It is particularly preferable that the modified polypropylene polymer has 0.1 to 2 wt% of maleic anhydride added, and the added amount is preferably 2 to 20 wt% in the total amount of PPG. This gives impact, rigidity,
The effect of improving strength is further improved. Also, the melt flow rate of polypropylene resin is 20 to 67 (g / 10 minutes)
Is preferred. If it is less than 20 (g / 10 minutes), the fluidity is poor and the glass fibers are raised on the surface, so that the surface gloss is lowered. On the other hand, when it exceeds 67 (g / 10 minutes), the weld rise becomes high, which is not preferable.

Next, the resin-coated glass fiber is a glass fiber coated with a thermoplastic resin in advance, and so to speak, corresponds to a glass fiber reinforced resin. This resin-coated glass fiber is usually preliminarily molded into a cylindrical pellet. This resin-coated glass fiber is usually obtained by impregnating and coating a roving glass fiber with a thermoplastic resin in an extruder or the like, extruding it into a strand shape, cooling and cutting it into pellets. Therefore, the glass fiber has the same length as the pellet. Specifically, it is marketed under the trade name of Celstran (manufactured by Polyplastics Co., Ltd.) and Burton (manufactured by ICI).

The resin-coated glass fiber preferably has a length of 1 mm to 20 mm. If it exceeds 20 mm, the height of the weld portion may increase. If it is less than 1 mm, impact strength and bending elasticity may be reduced. The diameter of the glass fiber in the resin-coated glass fiber is 10 to 25
It is preferably set to μm.

The thermoplastic resin forming the resin-coated glass fiber includes polypropylene, polyethylene, nylon and the like. Among these, polypropylene is the most preferable because it has good compatibility with the polypropylene as the component A. As the polypropylene resin, the same polypropylene resin as the component A can be used. Further, it is most preferable to use both polypropylene resins having the same composition and fluidity from the viewpoint of compatibility.

Further, the thermoplastic resin in the resin-coated glass fiber is 20% or more. If it is less than 20%, the glass fiber has poor sizing property and there is a problem in handling. The upper limit is preferably 70% from the economical point of view.

On the other hand, unlike the resin-coated glass fiber, the C component glass fiber is a single chopped strand glass fiber. Further, this is preferably surface-treated with aminosilane, epoxysilane, vinylsilane or the like. As a glass fiber, the diameter is 3 to 2
It is preferable to use one having a thickness of 0 μm. The length of the glass fiber is preferably 1 to 10 mm. 1m
If it is less than m, the impact strength and bending elasticity of the wheel cover are small, while if it exceeds 10 mm, the dispersion in the resin becomes poor.

The total amount G of glass fibers in the B and C components must be 5 to 35%. If it is less than 5%, the reinforcing effect by the glass fiber is insufficient, and the impact resistance is particularly low and it is not practical. On the other hand, if it exceeds 35%, the appearance quality (particularly weld rise) will not be improved even if the polypropylene resin is optimized. Also, more preferably, 15 to 3
It is 5%, and in this case, both mechanical properties and appearance quality are extremely good.

Further, from the viewpoint of appearance quality, it is particularly preferable that the amount of glass fibers in the B component is smaller than that of the C component. Further, the total amount of the synthetic resin component composed of the polypropylene resin as the component A and the thermoplastic resin as the component B is 65 to 95%. Further, the melt flow rate M (g / 10
Min) and the total amount G of the above glass fibers, M <100.
Must have a 0 / G relationship. If this relationship is broken, the height of the weld rise will increase.

Various methods are available for producing the composition of the present invention. The above components are pre-mixed with a Henschel mixer, a ribbon blender or the like and kneaded with a single screw extruder, a twin screw extruder, a kneader or the like. It is also possible to supply it to the machine for melt-kneading and granulation, or to supply only the glass fiber midway through the vent port of the extruder. In addition, the above composition relating to the present invention may contain various additives such as a heat stabilizer, a light stabilizer, an ultraviolet absorber, an antistatic agent, a lubricant, a flame retardant, and a colorant, if necessary. .

For fine adjustment of physical properties and costs, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, ethylene-based rubber such as ethylene-butene-1 copolymer rubber, styrene-butadiene rubber, etc.・ Elastomers such as styrene copolymer rubber, styrene-rubber such as styrene-ethylene / butylene-styrene copolymer,
It is possible to add various fillers such as talc, calcium carbonate, mica, barium sulfate, whiskers and clay.

[0020]

In the present invention, the above A, B and C
The total amount of synthetic resin components is 65 to 95%, the total amount G of glass fibers is 5 to 35%, and the relationship between the melt flow rate M of the polypropylene resin of component A and the total amount G of glass fibers is When M <1000 / G is satisfied,
The greatest feature is that it was found that the rising height of the weld portion in the molded wheel cover was reduced.

Further, by using the component B together, when comparing the physical properties of the material obtained by the prior art and the material obtained by the present invention with the same amount of glass fiber, the rise height of the weld portion is the same ( That is, the appearance quality is equivalent),
The synergistic effect of improving Izod impact strength, flexural modulus, and heat distortion temperature can be obtained. In other words, the amount of glass fiber added can be reduced under conditions that are equivalent to the physical properties, and the appearance quality of the wheel cover will be improved.

That is, when the compounding ingredients A, B and C of the present invention are melt-kneaded by using an extrusion kneader or the like, the component C is considerably damaged by the extrusion kneader or the like regardless of the fiber length at the raw material stage. Thus, the average fiber length becomes 400 to 500 μm. On the other hand, since the glass fiber length in the B component is covered with the thermoplastic resin, it is less likely to be damaged than the C component glass fiber. Therefore, even after the above kneading, the average fiber length is, for example, 7
It is as long as 00 to 800 μm.

Therefore, in the obtained wheel cover, as a result, a short glass fiber and a long glass fiber are mixed, and the short glass fiber plays a role of appearance quality and the long glass fiber plays a mechanical property. is expected. Therefore, the wheel cover has excellent mechanical properties such as impact strength and flexural modulus. Therefore, according to the present invention,
It is possible to provide a wheel cover that has a low weld height and has excellent appearance quality and mechanical properties.

[0024]

【Example】

Examples 1 to 7 The components A to C were mixed at various ratios (weight ratio), and 30
The mixture was melt-kneaded and granulated using a mm2 screw extruder, and then a molded product for testing (FIG. 2 described later) was injection molded using this (Examples 1 to 7). Bending elastic modulus (kg / cm ² ), heat distortion temperature (° C.), Izod impact strength at 23 ° C. (kg · cm / cm), weld height (μm), and gloss of the molded product. The degree (%) was measured.

The proportions of the above components and the measurement results are shown in Tables 1 and 2. For comparison, the table also shows that the relationship between the melt flow rate (MI) and the total amount of glass fibers (G) does not satisfy M <1000 / G (Comparative Examples 1 and 2) and resin-coated glass. The results obtained using no fibers (Comparative Examples 3 and 4) are also shown. The following components were used as the components shown in the table. As the polypropylene resin of the component A of the present invention, polypropylene and a modified polypropylene polymer were used.

As the former polypropylene, a crystalline ethylene / propylene / block copolymer containing 7% by weight of ethylene was used. Further, these have a melt flow rate (MI) of 15, 30, 45 or 80 (g / 10
Min) was used. As the modified polypropylene polymer, maleic anhydride modified crystalline polypropylene (homo) was used. Further, in Example 5, an ethylene / propylene copolymer rubber [propylene content 21
% By weight, Mooney viscosity 15 (ML _{1 + 4} 100 ° C)] 3
Used by weight% (Note 2 in Table 2).

Next, regarding the resin-coated glass fiber, a glass fiber having a diameter of 15 to 20 μm and a length of 6 to 7 mm and a bundle of the glass fiber impregnated and coated with a polypropylene resin as a thermoplastic resin was used. . This polypropylene resin is made of crystalline ethylene propylene having the melt flow rate of 45 (g / 10 minutes) shown in the above component A.
A block copolymer was used. The resin-coated glass fiber is a cylindrical pellet with a length of 6 to 7 mm (same as the glass fiber length) and a pellet diameter of 2 x 3 mm (oval).
Met. Further, the amount of glass fiber in the resin-coated glass fiber is 50% by weight.

However, the amount of glass fiber in the resin-coated glass fiber of Example 4 was 70% by weight (Note 1 in Table 2). Next, the C component glass fiber has a diameter of about 13 μm,
Chopped strands with a length of 3 mm were used. In Comparative Example C4, 15% chopped strands having the above diameter and length and 5% chopped strands having a diameter of about 13 μm and a length of 6 mm were used.

Further, in Tables 1 and 2, the column of resin-coated glass fiber indicates the total amount of the glass fiber and polypropylene resin constituting the resin, and the glass fiber accounts for 50% of the total amount as described above. is occupying. Therefore, in the column of the total amount G of glass fibers in the same table, the total amount (% by weight) of the glass fiber amount of 50% of the resin-coated glass fibers of the component B and the glass fiber amount of the component C is shown. ing.

Next, the flexural modulus shown in the table is ASTM-
D790, heat distortion temperature is ASTM-D648 (18.6).
kg / cm ² load), Izod impact strength is ASTM-
It was measured by D256 (notched). As for the ridge height of the weld portion, a box-shaped resin molded product was molded by the double gates 71 and 72 as shown in FIG. 2, and the ridge height L at the weld portion 93 was measured as shown in FIG. . A surface roughness meter [Surfton 550AD, Tokyo Seimitsu Co., Ltd.] was used for this measurement. The glossiness was measured according to JISK6758.

Next, the measurement results will be described. Table 1
And as is known from Table 2, Example 1 according to the present invention
In ~ 7, the rise height of the weld is 16 ~ 3
It is 3 μm, and it can be seen that the impact height and bending elastic modulus are also high. Particularly, in Example 5 in which the ethylene / propylene copolymer rubber was added, the swelling height was small and the impact strength was also high. On the other hand, Comparative Examples C1 and C2 have a large rising height, and Comparative Examples C3 and C4 have a small rising height but a low impact strength. That is, according to the present invention, it is possible to suppress the rising height to be low, increase the impact strength and the flexural modulus, and improve the glossiness.

[0032]

[Table 1]

[0033]

[Table 2]

Examples 11 to 19 Using 10% of resin-coated glass fiber (GF50 wt%),
In the same manner as in Example 1, a resin molded product was injection molded, and the relationship between the total amount G of glass fibers and the melt flow rate M (g / 10 minutes) of polypropylene resin (PP) at that time is shown in FIG. Plotted. Then, the rising height (μm) of the weld portion in each example is calculated as in Examples 11 to 11.
Number 19 is the value enclosed by a circle (○), and Comparative Example C
11 to C16 are shown by numerical values surrounded by squares (□).

As can be seen from the figure, in Examples 11 to 19 according to the present invention, the rising height is less than 33 μm,
On the other hand, the comparative examples C11 to C13, C15, and C16 have a rise height of 37 or more. At the boundary between the two, a relation line of M = 1000 / G can be drawn as shown in FIG. In addition, in Comparative Example C14, the total amount G of glass fibers is 40%, and the rise height is 39 μm.
From the above, M <1000 / G, glass fiber total 35%
In the following cases, it can be seen that the swelling height is 35 μm or less.

Test Example Using PPG shown in Examples 1 to 7 and Comparative Examples C1 to C4, a wheel cover (see FIG. 4) was injection molded and a product test was conducted. The results are shown as wheel cover product Nos. Using the compositions corresponding to the respective examples and comparative examples. The results are shown in Tables 3 and 4. The wheel cover had the shape shown in FIG. 4, had a diameter of 39 cm, an average wall thickness of 2.5 mm, and had a total of six fan-shaped air holes.
Moreover, the size of one air hole is about 6 cm x 3.5 cm x 4
It was cm.

The tests, product appearances, and comprehensive evaluations shown in "Items" of each table were carried out as follows. (1) Repeated detachment / attachment test: Repeated detachment / attachment of the wheel cover to / from the wheel disc to investigate occurrence of defects such as cracks. ○: No problem such as cracking even after 30 times of desorption

(2) Heat resistance test The wheel cover was put in a constant temperature bath at 120 ° C., and the dimensional change, deformation, etc. after 24 hours were measured. ◯: No significant thermal deformation ×: Practically harmful thermal deformation (3) Falling ball test At 23 ° C, a 500 g rope ball was dropped naturally on the design surface of the wheel cover. ○: No crack at 50 cm ×: Crack at 40 cm or less

(4) Product Appearance Visual evaluation of the swelling state and gloss of the weld portion on the design surface of the wheel cover 1; Beautiful swelling of the weld portion is rare. 2; Beautiful, there is a slight rise in the weld area, but there is no practical problem. 3; The gloss is low and the swelling of the weld is conspicuous.
Not practical.

As is apparent from both tables, the wheel covers according to the present invention (Product No., Examples 1 to 7) are extremely excellent in product appearance.

[0041]

[Table 3]

[0042]

[Table 4]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a rising height of a weld portion in a relationship between a total amount of glass fibers and a melt flow rate of polypropylene resin in an example.

FIG. 2 is an explanatory view of a weld portion in the embodiment.

FIG. 3 is an explanatory view of a height of a weld portion rising along a line YY of FIG.

FIG. 4 is an explanatory view of a weld portion in the wheel cover shown in the conventional example.

FIG. 5 is an explanatory view of the rise of the weld portion shown in the conventional example.

[Explanation of symbols]

 8. ． ． Excitement, 82. ． ． Glass fiber, 9. ． ． Wheel cover, 93. ． ． Weld part,

Claims (1)

[Claims] 1. A wheel cover to be mounted on a wheel of an automobile, the wheel cover being coated with (A) a polypropylene resin and (B) a thermoplastic resin of 20% (weight ratio, hereinafter the same) or more in advance. Resin-coated glass fiber and (C) glass fiber, and the total amount of the synthetic resin component in the components (A) and (B) is 65 to 95%, and (B) and (C). ) The total amount G of glass fibers in the component is 5 to 35%, and the melt flow rate M (g / 10 min) of the polypropylene resin of the component (A) and the total amount G of the glass fibers are
(% By weight) is a wheel cover formed of a glass fiber reinforced polypropylene resin composition that satisfies the relationship of M <1000 / G.