JP2008279787A - Molding for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding for automobile capable of suppressing contraction after molding greatly without applying annealing treatment for a long time. <P>SOLUTION: In a door waist molding having a main body part 2 made of polypropylene being olefin-based thermoplastic resin, the whole periphery of an inner layer 12a made of polypropylene containing organic filler of 30-50 wt.% is covered with an outer layer 12b made of polypropylene containing inorganic filler of 30-50 wt.%. The organic filler is any of wood chips made of plants, paper dust, and cellulose, and the inorganic filler is any of calcium carbonate, talc, and wollastonite. A ratio of cross sectional area of the outer layer 12b to the inner layer 12a is 1:2, and the position of the center of gravity of the inner layer 12a agrees with the position of the center of gravity of the outer layer 12b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is mounted around an automobile molding, for example, a door waist molding (belt line molding) attached to a waist portion (belt line) of a side door, a roof molding attached to a rule side portion, or a windshield glass. In particular, the present invention relates to a structure of an automobile molding that takes into account dimensional changes due to contraction and expansion in the longitudinal direction.

In this type of automotive molding, it is common to have, for example, a skin layer, a protective layer for decoration, various lips, etc. in addition to the molding body. In the part, in consideration of weight reduction and recyclability of itself, instead of embedding a metal core inside, as described in Patent Documents 1 to 3, For example, when molding with an olefin thermoplastic resin such as polypropylene or a styrene thermoplastic resin, a powdery or filler-like inorganic auxiliary material such as mica, talc, or glass fiber is blended in consideration of weather resistance. Composite materials are used. In particular, polypropylene blended with talc is called talc PP and is being used widely as a material for the molding body.
JP-A-11-227457 JP 2000-117808 A JP 2003-266514 A

  However, in composite materials represented by so-called talc PP, shrinkage due to changes in environmental load conditions such as a thermal cycle is remarkable, and the original function of the molding body is impaired after being mounted on the vehicle body as a molding. Or secondary defects such as poor appearance are likely to occur.

  As a countermeasure against such secondary defects, it is possible to suppress the shrinkage to some extent by performing annealing after completion as a molding, but if processing is attempted until the shrinkage converges to a practical level, the processing time Becomes extremely long, and the productivity is remarkably lowered.

  The present invention has been made paying attention to such problems, and in particular, provides an automotive molding structure capable of significantly suppressing shrinkage after molding without performing a long-time annealing treatment. Is.

  The invention according to claim 1 is a long automotive molding in which the main body portion is made of an olefinic thermoplastic resin, and the main body portion includes an inner layer of an olefinic thermoplastic resin containing 30 to 50 wt% of an organic filler, And an outer layer of an olefin-based thermoplastic resin containing 30-50 wt% of an inorganic filler, wherein the entire circumference of the inner layer is covered with the outer layer.

  The reason why the content of each filler is 30 to 50 wt% is that it is not suitable for long molding because the linear expansion coefficient is too large if it is less than 30 wt%, and the specific gravity is too high if it exceeds 50 wt%, This is because the impact resistance is also lowered, so that it is not suitable for molding.

  The organic filler is desirably derived from a plant as described in claim 2, and more specifically, as described in claim 3, the organic filler is made of wood powder, paper powder and cellulose. And the inorganic filler is at least one of calcium carbonate, talc and wollastonite. Of course, two or more kinds of organic fillers and inorganic fillers can be mixed and used.

  As the olefinic thermoplastic resin, as described in claim 4, polypropylene is particularly desirable in terms of moldability and cost.

  Here, in the inventions according to claims 1 and 2, the combination of the organic filler and the inorganic filler is that the organic filler such as wood flour has an expansibility due to fluctuations in environmental load conditions such as a cooling cycle. This is because the inorganic filler such as talc exemplified above has a characteristic of contracting due to a change in environmental load conditions such as a thermal cycle.

  In this case, considering the balance between shrinkage and expansion when subjected to fluctuations in environmental load conditions such as a thermal cycle, the cross-sectional area ratio between the outer layer and the inner layer is, for example, 1: 2 as described in claim 5. It is more desirable, and the center of gravity of the inner layer matches the position of the center of gravity of the outer layer in the cross section orthogonal to the longitudinal direction of the main body portion as described in claim 6. It is more desirable to suppress the occurrence of molding warpage by combining the center of force and the center of force to expand.

  Therefore, in at least the invention of claim 1, the inner layer of the molding main part is an olefin-based thermoplastic resin containing an expandable organic filler, while the outer part of the main part is also shrinkable. Because it is an olefin-based thermoplastic resin containing an inorganic filler, the shrinkage and expansion of the molding body are offset when subjected to fluctuations in environmental load conditions such as cooling and cooling cycles. Dimensional change in the longitudinal direction due to can be greatly suppressed. At the same time, since the outer layer covers the entire circumference of the inner layer, a change in the cross-sectional shape due to the difference between shrinkage and expansion can be suppressed, and as a result, the occurrence of warpage in the longitudinal direction can also be suppressed.

  According to the first to fourth aspects of the present invention, even if the environmental load conditions such as the thermal cycle are affected by the offset effect between the expandable organic filler and the shrinkable inorganic filler, The dimensional change in both the longitudinal direction and the cross-sectional shape is extremely small, and the dimensional change of a long molding due to secular change or aging can be greatly suppressed.

  According to the fifth aspect of the present invention, the balance between shrinkage and expansion when subjected to fluctuations in environmental load conditions such as a thermal cycle is achieved by setting the cross-sectional area ratio between the outer layer and the inner layer to a specific ratio. This is more advantageous in suppressing the above dimensional change.

  According to the sixth aspect of the present invention, in order to obtain an offset effect between the organic filler having the expandability and the inorganic filler having the contractibility as described above, the center of force to be contracted and the center of the force to be contracted are to be expanded. Since the center of force can be matched, there is an advantage that the occurrence of molding warpage can be further suppressed.

  FIG. 1 is a view showing a more specific embodiment of an automobile molding according to the present invention, and shows an example of a door waist molding (belt line molding) 1 attached to a door waist portion (belt line).

  The door waist molding 1 is formed so that the cross-sectional shape of FIG. 1 is a uniform long shape in the longitudinal direction, and a flat leg portion 3 and a cover portion 4 that is curved from one end of the leg portion 3. And a main body portion 2 which is a main body portion bent into a substantially bowl shape. A holding bead portion 5 and a holding lip 6 are integrally formed on the inner side surfaces of the leg portion 3 and the cover portion 4 so as to face each other in two steps, and the cover portion 4 is made of a skin layer 7. In addition to being covered, a panel lip 8 protrudes from the tip of the cover portion 4. The holding bead portion 5 and the holding lip 6 fit and hold a door outer panel (not shown) at the door waist opening, and the panel lip 8 comes into pressure contact with the door outer panel.

  On the other hand, a seal lip 9 is integrally formed on the outer surface of the leg 3 in two upper and lower stages, and an auxiliary lip 10 is integrally formed. The seal lip 9 is directly formed on a door glass (not shown). In order to be elastically contacted, a flocked layer 11 is formed on a portion sliding with the door glass.

  Here, as described above, the main body portion 2 including the leg portion 3 and the cover portion 4 is formed by the inner layer 12a and the outer layer 12b covering the entire circumference of the inner layer 12a, and the leg portion 3 is formed in the circumferential direction. Every position has a so-called three-layer sandwich structure, and the cover portion 4 covered with the skin layer 7 has a four-layer structure. The door waist molding 1 having such a cross-sectional structure is formed by a known coextrusion molding method.

  The main body 2 has a composite structure by combining different materials of the inner layer 12a and the outer layer 12b, and the inner layer 12a is made of a so-called plant-derived organic system in polypropylene as an olefinic thermoplastic resin that is a matrix resin. Whereas the outer layer 12b is formed of a resin material containing 30 to 50 wt% of at least one of wood powder, paper powder and cellulose alone as a filler, the outer layer 12b is an olefin-based heat which is also a matrix resin. It is formed of a resin material containing 30 to 50 wt% of at least one of calcium carbonate, talc and wollastonite as an inorganic filler in polypropylene as a plastic resin.

  In addition to the seal lip 9 and the auxiliary lip 10, the holding lip 6, the holding bead portion 5, and the panel lip 8 are formed of an olefin-based or styrene-based thermoplastic elastomer having a hardness of 60A to 80A, for example. The skin layer 7 is made of a thermoplastic resin or a decorative film having good affinity with the cover portion 4.

  As described above, the outer layer 12b formed of polypropylene containing inorganic fillers such as calcium carbonate, talc, and wollastonite is so-called shrinkage that shrinks when subjected to fluctuations in environmental load conditions such as a thermal cycle. In contrast, the inner layer 12a formed of polypropylene containing plant-derived organic fillers such as wood powder, paper powder, and cellulose was subject to fluctuations in environmental load conditions such as a thermal cycle. It has a so-called expansibility that expands in some cases. In the present embodiment, the outer layer 12b having contractibility and the inner layer 12a having expandability are actively combined and formed integrally in a laminated structure, thereby attempting to expand with the force to contract. Thus, the aging change of the door waist molding 1 as a product or the dimensional change due to aging is suppressed.

  Further, the thickness of the outer layer 12b covering the entire circumference of the inner layer 12a is made uniform, the contour shape of the inner layer 12a and the contour shape of the outer layer 12b are substantially similar, and the outer layer 12b and the inner layer 12a. In order to suppress the above dimensional change by setting the cross-sectional area ratio, and considering the initial elastic modulus, shrinkage rate, expansion rate, etc. of each material, the force to shrink and the force to expand balance the inner and outer layers The cross-sectional area ratio between the outer layer 12b and the inner layer 12a is set to a predetermined value so that the thicknesses of 12a and 12b can be balanced. More specifically, the value obtained by multiplying the initial elastic modulus of the outer layer 12b by the shrinkage rate and the cross-sectional area is set so that the value obtained by multiplying the initial elastic modulus of the inner layer 12a by the expansion coefficient and the cross-sectional area is substantially equal to each other. To do.

  Here, the cross-sectional area ratio between the outer layer 12b and the inner layer 12a is set to 1: 2, for example, so that the center of gravity position of the inner layer 12a and the center of gravity of the outer layer 12b in the sectional shape of FIG. is there. This suppresses the dimensional change in the cross-sectional shape of FIG. 1 by offsetting the force for contraction and the force for expansion described above, thereby suppressing the warp in the longitudinal direction of the door waist molding 1. Based on trying.

  However, it goes without saying that the cross-sectional area ratio between the outer layer 12b and the inner layer 12a is not limited to 1: 2 as exemplified above, depending on the combination of the organic filler content and the inorganic filler content. .

  In addition, the content of each filler is set to 30 to 50 wt% regardless of whether it is organic or inorganic, because the linear expansion coefficient becomes too large if it is less than 30 wt%. This is because it is not suitable for the door waist molding 1 because the specific gravity is too high and the impact resistance is lowered when it exceeds 50 wt%.

  Table 1 shows changes in dimensions when a polypropylene containing an inorganic filler is extruded into a test piece having a width dimension of 35 mm and a thickness of 2 mm, and a thermal cycle test is performed using the test piece as a test piece.

  Similarly, Table 2 shows dimensional changes when a polypropylene containing an organic filler is extruded into a test piece having a width dimension of 35 mm and a thickness of 2 mm, and a thermal cycle test is performed using the test piece as a test piece. The thermal cycle test was performed for 20 cycles, with -30 ° C. × 4 hr → 23 ° C. × 30 min → 80 ° C. × 4 hr as one cycle.

  As is clear from Tables 1 and 2, talc, calcium carbonate, and wollastonite, which are inorganic fillers, all exhibit similar shrinkage, and shrinkage decreases as the amount of filler added increases. There is a tendency. On the other hand, cellulose, wood flour, and paper, which are plant-derived organic fillers, all exhibit similar expansibility, but there is a tendency that the expansion rate does not fluctuate greatly even if the amount of filler added is increased or decreased.

  The present inventor uses polypropylene as the matrix resin for the inner and outer layers 12a and 12b, and in addition to the combination of the organic filler contained in the inner layer 12a and the inorganic filler contained in the outer layer 12b, their addition amount and cross-sectional area. The door waist molding 1 having a cross-sectional shape as shown in FIG. 1 was extruded by varying the ratio. And the thermal cycle test of those door waist moldings 1 was done. The conditions for the thermal cycle test were the same as in the previous case. The results are shown in Table 3.

  The comparative example in Table 3 is equivalent to the conventional product, and is extruded with polypropylene containing 30 wt% of talc, which is an inorganic filler, without distinction between the inner and outer layers 12a and 12b.

  In Examples 1 and 2, the combination of talc, which is an inorganic filler to be included in the outer layer 12b, and cellulose, which is an organic filler to be included in the inner layer 12a, and the content (addition amount) thereof is 50. Both are the same at / 40, but the cross-sectional area ratios of the inner and outer layers 12a and 12b are changed. As is clear from Examples 1 and 2, in the combination of talc and cellulose, the shrinkage rate as the door waist molding 1 is significantly reduced as compared with the comparative example, and the cross-sectional area ratio between the outer layer 12b and the inner layer 12a. When the cross-sectional area ratio is 1: 2, the shrinkage rate as the door waist molding 1 is further reduced as compared with the case where the ratio is 1: 1.

  In Examples 2 to 6, the combination of talc, which is an inorganic filler to be included in the outer layer 12b, and cellulose, which is an organic filler to be included in the inner layer 12a, is the same, but the contents of both In the range of 30-50 wt percent. In Example 3 where the filler content is relatively small regardless of whether it is inorganic or organic, the shrinkage rate as the door waist molding 1 tends to be larger than the others, but other than that In each embodiment, the shrinkage rate as the door waist molding 1 is significantly reduced. However, even in the case of the third embodiment, the door waist molding 1 can be formed from a material having a specific gravity lower than that of the conventional one, which is particularly advantageous in terms of weight reduction of the molding alone.

  In Examples 7 to 10, on the contrary, although the contents of the inorganic filler and the organic filler are the same, the inorganic filler to be included in the outer layer 12b and the organic filler itself to be included in the inner layer 12a. The combination of is changed. In any case, it can be understood that the shrinkage rate is greatly reduced.

  Thus, in each of the examples, particularly in cases other than Examples 3 and 4, the shrinkage rate is about 0.01 to 0.03%, which can be close to zero. This is because when the door waist molding 1 is mounted on a vehicle, not only does the positional deviation at the longitudinal end portion not occur due to secular change, but also there is no gap or step between the door panel. Meaning and is very useful in practice.

  FIG. 2 shows a second embodiment of the present invention, showing an example in which the present invention is applied to a roof molding 21 to be mounted on a roof of a vehicle body. It is attached.

  The roof molding 21 is fitted into a concave groove formed at a joint between a roof panel and a body side (not shown), and a skin layer 25 serving as a design surface of the head 23 is substantially the same as the roof panel. The groove is fitted and held so as to be flush with each other. The head 23 including the holding lip 26 and the leg 24 including the holding lip 27 are formed of an olefin-based or styrene-based thermoplastic elastomer, whereas they are interposed between the head 23 and the leg 24. A molding main body portion 22 which is a main body portion is formed of an inner layer 12a and an outer layer 12b using different inorganic fillers and organic fillers similarly to FIG.

  Therefore, also in the second embodiment, the same effect as in the first embodiment can be obtained.

  In addition, it cannot be overemphasized that this invention is applicable similarly to the same kind of malls other than the door waist molding, roof molding, and wind molding which were illustrated previously.

Sectional drawing which shows the structure of a door waist molding as 1st Embodiment of the molding which concerns on this invention. Sectional drawing which shows the structure of a roof molding as 2nd Embodiment of the molding which concerns on this invention.

Explanation of symbols

1 ... Door waist molding 2 ... Main part (main part)
DESCRIPTION OF SYMBOLS 3 ... Leg part 4 ... Cover part 6 ... Holding lip 7 ... Skin layer 9 ... Seal lip 11 ... Flocking layer 12a ... Inner layer 12 ... Outer layer 21 ... Roof molding 22 ... Mall main part (main part)
23 ... Head 24 ... Leg 25 ... Skin layer

Claims (6)

In long automotive moldings where the body is made of olefinic thermoplastic resin,
The main body portion is composed of an inner layer of an olefinic thermoplastic resin containing 30-50 wt% of an organic filler, and an outer layer of an olefinic thermoplastic resin containing 30-50 wt% of an inorganic filler,
An automotive molding characterized in that the entire circumference of the inner layer is covered with the outer layer.   The automotive molding according to claim 1, wherein the organic filler is derived from a plant.   The organic filler is at least one of wood powder, paper powder, and cellulose, and the inorganic filler is at least one of calcium carbonate, talc, and wollastonite. The automobile molding according to claim 2.   4. The automotive molding according to claim 3, wherein the olefinic thermoplastic resin is polypropylene.   The automotive molding according to claim 4, wherein a cross-sectional area ratio between the outer layer and the inner layer is 1: 2.   6. The automotive molding according to claim 5, wherein the center of gravity of the inner layer and the center of gravity of the outer layer are matched in a cross section orthogonal to the longitudinal direction of the main body portion.

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