Extrusion moldings, weather strips

Abstract

To provide an extrusion molded product and a weather strip that contribute to weight reduction and facilitate obtaining desired rigidity and linear expansion coefficient.SOLUTION: A kneaded material obtained by blending a polypropylene resin composition with a plate-shaped particle inorganic filler and a foaming agent is extrusion-molded, and the foaming agent is foamed by the extrusion molding to obtain an extrusion molded product. In the kneaded material, a weight ratio (polypropylene resin composition / inorganic filler) of the polypropylene resin composition and the inorganic filler is set in a range of 50 / 50 to 95 / 5. A weather strip W is composed of a mounting base 1 which is made of the extrusion molded product and can be freely fitted to a vehicle body of an automobile, and elastic portions 2, 3 which are made of a thermoplastic elastomer molded product obtained by extrusion molding of a thermoplastic elastomer composition and can be freely in contact with a door glass G provided on a door panel .SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an extrusion molding, a weatherstrip, and relates to a technique applicable to weatherstrips attached to the body of an automobile (for example, weatherstrips attached to the door waist). [Background technology]

[0002] For example, extrusion moldings such as weather strips (such as door waist weather strips) attached to the body of an automobile are required to be lightweight so as to contribute to improving the fuel efficiency of the automobile.

[0003] One example of weight reduction is a method of designing the cross-sectional shape of the extrusion molded body to be smaller, but this method may impair the ability of the extrusion molded body to conform to the attachment location (e.g., a location that can be freely attached so as to fit onto a vehicle body, etc.; hereinafter simply referred to as the attachment location). In this case, it may be possible to address the issue by changing the design of the attachment location itself, but such a design change would increase the cost of the vehicle body, and is therefore not realistic. Therefore, in the case of a method of designing the cross-sectional shape of the extrusion molded body to be smaller, the degree of freedom in design is limited (limited depending on the shape of the attachment location, etc.), making it difficult to achieve sufficient weight reduction.

[0004] Patent Document 1 discloses an extrusion molded product (hereinafter simply referred to as a TPE foam molded product) that is made by extruding a kneaded product obtained by compounding a relatively flexible thermoplastic elastomer (Milastomer (registered trademark) M440B manufactured by Mitsui Chemicals, Inc.) with an inorganic filler, a foaming agent, etc., and foaming the kneaded product. This type of TPE foam molded product has a lower specific gravity than, for example, an unfoamed extrusion molded product (a molded product formed without using a foaming agent, etc.; hereinafter simply referred to as a solid molded product), and therefore may be able to achieve the desired weight reduction without the need for the aforementioned design to reduce the cross-sectional shape. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4298447 Summary of the Invention [Problem to be solved by the invention]

[0006] However, since the TPE foam molded article in Patent Document 1 does not take into consideration rigidity or linear expansion coefficient, it may not be possible to obtain the required properties (for example, the properties required when used as a weatherstrip).

[0007] For example, if the rigidity of the TPE foam molding is too high, there is a risk of so-called cracking (for example, cracks, fissures, etc. occurring during secondary processing of the TPE foam molding (for example, when cutting both ends in the longitudinal direction) or when installing), or unintended plastic deformation (deformation such as warping) may occur, making it difficult to install at the installation location.

[0008] Furthermore, if the linear expansion coefficient of the TPE foam molding is too high, even if it can be attached to the attachment location, the dimensions of the TPE foam molding may change depending on the temperature environment. In this case, an unintended gap (for example, a gap that may be formed due to dimensional changes caused by temperature changes after attachment) may occur between the TPE foam molding and the attachment location, resulting in a loss of conformability.

[0009] The present invention has been made in consideration of the above-mentioned technical problems, and aims to provide an extrusion molded product and weather strip that contribute to weight reduction and make it easier to obtain the desired rigidity and linear expansion coefficient. [Means for solving the problem]

[0010] The extrusion molded article and weatherstrip of this invention can contribute to solving the above-mentioned problems, and one embodiment of the extrusion molded article is an extrusion molded article obtained by extruding a kneaded product in which a polypropylene resin composition is blended with a plate-like inorganic filler particle and a foaming agent, and the foaming agent is foamed by the extrusion molding, and the kneaded product is characterized in that the weight ratio of the polypropylene resin composition to the inorganic filler, that is, polypropylene resin composition / inorganic filler, is within the range of 50 / 50 to 95 / 5.

[0011] The foaming agent may be any one of microcapsules, an organic foaming agent, and a supercritical fluid foaming agent, and the cell diameter of foam cells formed in the extrusion molded body by foaming the foaming agent may be within the range of 50 μm to 200 μm.

[0012] One aspect of the weatherstrip is characterized in that it comprises the extruded body described above, and the extruded body is assembled to a vehicle body.

[0013] One aspect of the weatherstrip may be characterized by comprising: a mounting base made of the extrusion molded body and capable of being freely fitted to a door panel that is part of the body of an automobile; and an elastic portion made of a thermoplastic elastomer molded body obtained by extrusion molding a thermoplastic elastomer composition and capable of being freely in elastic contact with the door glass provided on the door panel. [Effects of the Invention]

[0014] According to the present invention, it is possible to contribute to weight reduction and to easily obtain the desired rigidity and linear expansion coefficient. [Brief explanation of the drawings]

[0015] [Figure 1] Schematic diagrams for explaining the internal structure of the extrusion-molded body according to the present invention ((A) shows a structure in which foam cells F are supported by a polypropylene resin composition or the like, and (B) shows a state in which foam cells F are surrounded by polypropylene molecules). [Figure 2] Schematic configuration diagram (radial cross-sectional view) for explaining the weatherstrip W, which is an application example of the PP foam molded body according to the embodiment.

Mode for Carrying Out the Invention

[0016] The extrusion molded body and weatherstrip of the embodiment of the present invention are completely different from the TPE foam molded body as shown in Patent Document 1.

[0017] That is, the extrusion molded body and weatherstrip of the present embodiment are formed by extruding a kneaded product in which a plate-like particle inorganic filler and a foaming agent are blended into a polypropylene resin composition (hereinafter, simply referred to as a PP kneaded product as appropriate), and the foaming agent is foamed by the extrusion molding (hereinafter, simply referred to as a PP foam molded body as appropriate). The PP kneaded product applied to this PP foam molded body has a polypropylene resin composition / inorganic filler in the range of 50 / 50 to 95 / 5.

[0018] In the case of an extrusion molded body different from the present embodiment, for example, a solid molded body formed by simply extruding a polypropylene resin composition or by extruding a kneaded product in which a large amount of inorganic filler is blended into the polypropylene resin composition (that is, a solid molded body molded without using a foaming agent; hereinafter, simply referred to as a PP solid molded body as appropriate), there is a risk that the rigidity becomes too high or the linear expansion rate becomes too large. For example, even if it is applied as a weatherstrip, it is considered that the required characteristics cannot be obtained.

[0019] On the other hand, according to the PP foam molded body applying a PP kneaded product in which the polypropylene resin composition / inorganic filler is in the range of 50 / 50 to 95 / 5 as in the present embodiment, since foam cells are dispersed and formed in the PP foam molded body, for example, compared with a PP solid molded body, the content ratio of the polypropylene resin composition (the region of the polypropylene resin composition in the PP foam molded body) becomes small, the specific gravity is reduced, and the elastic modulus becomes large. In addition, the temperature dependence due to the polypropylene resin composition is suppressed.

[0020] In addition, the crystallinity of the polypropylene resin composition after extrusion molding (after cooling) is also suppressed, In PP foamed moldings, the inorganic filler is distributed so that it is oriented along the extrusion direction, which prevents the rigidity from becoming too high compared to PP solid moldings, and also makes it easier to achieve the desired elasticity.

[0021] Furthermore, the linear expansion coefficient of the PP foamed molded product reflects not only the linear expansion coefficient of the polypropylene resin composition but also the linear expansion coefficient of the inorganic filler (i.e., a linear expansion coefficient that is relatively lower than that of the polypropylene resin composition), and therefore, compared to the PP solid molded product, the linear expansion coefficient is suppressed from becoming too large.

[0022] Therefore, the PP foam molded article of this embodiment not only contributes to weight reduction, but also facilitates achieving the desired rigidity and linear expansion coefficient. This prevents so-called cracking and unintended plastic deformation, improving productivity and product yield. It also prevents dimensional changes due to temperature environments, ensuring that conformability is not impaired. Furthermore, when applied as a weatherstrip, for example, it is fully possible to obtain the required properties.

[0023] The extrusion molded article and weatherstrip of this embodiment may be a PP foam molded article using a PP kneaded product in which the polypropylene resin composition / inorganic filler ratio is in the range of 50 / 50 to 95 / 5, as described above, and various design modifications are possible. That is, the design can be modified by appropriately applying common technical knowledge in various fields (for example, the extrusion molding field, the weatherstrip field, the resin composition field, etc.) and by appropriately referring to prior art documents, etc. as necessary, and the following examples are given as examples.

[0024] Example <PP発泡成形体に適用可能なPP混練物> In the PP kneaded product applied to the PP foam molded body, it is a kneaded product in which a polypropylene resin composition, an inorganic filler, and a foaming agent are blended and kneaded as appropriate, and any material that can be extrusion molded into a desired shape is acceptable, and various additives may be blended according to the purpose.

[0025] <Polypropylene resin composition> As an example of the polypropylene resin composition, those composed of homopolymer type, random copolymer type, and block copolymer type polypropylene can be mentioned, and they can be appropriately selected and applied according to the purpose.

[0026] <Inorganic filler> As an example of the inorganic filler, those composed of plate-like particles with a particle size of about several micrometers (5 μm to 6 μm in the verification described later) can be mentioned, and a specific example is talc (magnesium hydrosilicate). Such an inorganic filler will be distributed in the PP foam molded body so as to be oriented along the extrusion molding direction.

[0027] Each plate-like particle of the inorganic filler in the PP foam molded body has a decreasing mechanical strength as it approaches the outer peripheral edge of the plate-like particle. Therefore, if the blending amount of the inorganic filler becomes too large, it may affect the impact resistance of the PP foam molded body, so it is necessary to appropriately set the blending amount of the inorganic filler.

[0028] Specifically, in the polypropylene resin composition / inorganic filler, it can be appropriately set so as to be in the range of 50 / 50 to 95 / 5, preferably in the range of 85 / 15 to 95 / 5.

[0029] <Foaming agent> As an example of the foaming agent, microcapsules, organic foaming agents, and supercritical fluid foaming agents that can foam when the PP kneaded product is extrusion molded can be mentioned, and they can be appropriately selected and applied within a range that does not overly damage the appearance and rigidity of the target PP foam molded body.

[0030] For example, the cell diameter of the foam cells formed in the PP foam molded body due to the foaming of the foaming agent is about several tens of micrometers to several hundreds of micrometers (the degree to which a microcellular foam can be obtained; 50 μm to 200 μm in the verification described later), or the foaming ratio compared to the PP solid molded body is less than 2 (in the verification described later, about 1.7 or less, preferably about 1.35 or less). These are examples of applications.

[0031] According to the PP foam molded body obtained by applying the foaming agent in this way, as shown in FIG. 1 for example, adjacent ones of each foam cell (reference numeral F in FIG. 1) are mutually supported by other components (for example, polypropylene resin composition or inorganic filler; reference numeral R in FIG. 1), forming a so-called strut structure. As a result, in terms of the rigidity of the PP foam molded body, even if it is lower compared to the PP solid molded body, it can be maintained to an extent according to the purpose (for example, the extent required for a weather strip).

[0032] <Configuration example of PP foam molded body> By extrusion-molding the PP kneaded product into a shape according to the purpose, various PP foam molded bodies can be configured. As an example, a weather strip or the like assembled to an automobile body can be mentioned.

[0033] Also, instead of simply extrusion-molding the PP kneaded product, it may be extrusion-molded (co-extrusion molding) together with other materials (for example, an olefin-based thermoplastic elastomer composition, etc.). As an example, weather strips such as an inside seal, an outside seal, and a belt mold attached to a door waist opening of a door panel (for example, an opening provided with a lifting or non-lifting door glass) can be mentioned.

[0034] The weather strip W shown in FIG. 2 is formed by co-extrusion molding a PP kneaded product and a thermoplastic elastomer composition, and shows an example of a configuration attached to the indoor side of a door waist opening (detailed illustration is omitted).

[0035] This weatherstrip W is mainly composed of a PP foam molded body obtained by extrusion molding a PP kneaded product, which has a mounting base 1 that can be fitted to the door waist opening, and a thermoplastic elastomer molded body obtained by extrusion molding a thermoplastic elastomer composition, which has upper and lower seal lip portions (elastic portions) 2 and 3 that can be elastically contacted with the door glass G of the door waist opening.

[0036] The mounting base 1 has a deformed U-shaped cross-sectional shape in the radial direction and is configured to be detachably fitted and attached to the door inner panel 4a and the rain reinforcement 4b.

[0037] At the center of one side wall portion 11 of the mounting base 1 located on the door glass G side, a support portion 12 for supporting the seal lip portions (elastic portions) 2 and 3 is integrally formed. This support portion 12 has a support base portion 12a that protrudes from the center of the side wall portion 11 toward the door glass G side, and an extension base portion 12b that extends in the vertical direction from the tip of the support base portion 12a.

[0038] On the inner peripheral surface of the mounting base 1, a plurality of fine retaining lips 13 and bead portions 14 are appropriately formed in consideration of the detachability and fitting retention to the door inner panel 4a and the rain reinforcement 4b. Also, on the outer peripheral surface of the mounting base 1, a bead portion 15 is appropriately formed at a position facing the door trim D. This bead portion 15 is not limited to the description in FIG. 2, and any mode that can be appropriately engaged with the door trim D when the weatherstrip W is attached to the door waist opening is acceptable.

[0039] The seal lip portions 2 and 3 are integrally formed so as to extend obliquely upward toward the door glass G on both end sides in the extending direction of the extension base portion 12b. In the case of the seal lip portions 2 and 3 in FIG. 2, the base side (extension base portion 12b side) has a thin-walled shape and is shaped so as to be bendable and deformable with the base side as a fulcrum. In the portions of the seal lip portions 2 and 3 that are elastically in contact with the door glass G, for example, pile layers 2a, 3a, etc. as shown in FIG. 2 may be formed in consideration of slidability and the like.

[0040] According to the weatherstrip W as described above, the seal lip portions 2 and 3 elastically contact the door glass G while being bent and deformed, and it becomes possible to exhibit a predetermined sealing function.

[0041] <Verification> Next, using PP kneaded products with the compounding amounts shown in Table 1 below, samples of PP foam molded bodies (samples S1 to S6 of the examples and sample Q of the comparative example) having the same shape as the weatherstrip W shown in FIG. 2 were prepared. Then, in samples S1 to S5 and Q, the physical properties (specific gravity, expansion ratio, appearance, cell diameter of the foam cells, surface roughness, tensile rigidity, linear expansion coefficient) of the items shown in Table 1 were examined respectively.

[0042] In addition, as reference examples corresponding to samples S1 to S5 and Q respectively, samples S1α to S1α and Qα of PP solid molded bodies were also prepared, and their compounding amounts and physical properties are also shown in Table 1. Also, among the physical properties in Table 1, in the item of appearance, the observation results by visual inspection are shown. The symbol "◎" indicates that no fraying or the like was found and good appearance was obtained. The symbols "△, ○" indicate cases where fraying or the like was slightly found but sufficient appearance (inferior to the case of the symbol "◎" but sufficient appearance) was obtained.

[0043]

Table 1

[0044] Therefore, the PP kneaded product used in the samples S1 to S5 of the examples and the thermoplastic elastomer composition were simultaneously extrusion-molded to produce the weatherstrip W shown in FIG. 2, and when it was actually applied to the door waist opening of the door panel, it was confirmed that various characteristics required for the weatherstrip W (such as the followability of the mounting base 1 to the door waist opening, the sealing performance of the seal lip portions 2 and 3, and the rainwater wiping performance) were satisfied.

Explanation of Reference Numerals

[0045] W... Weatherstrip 1... Mounting base 2, 3... Seal lip portions

Claims

A weatherstrip comprising an extruded molded article in which a foaming agent is foamed by extruding a kneaded product in which a plate-like particle inorganic filler and a foaming agent are blended into a polypropylene resin composition, and the extruded molded article is assembled to a vehicle body, wherein the kneaded product has a weight ratio of polypropylene resin composition / inorganic filler, which is the weight ratio of the polypropylene resin composition to the inorganic filler, in the range of 85 / 15 to 95 / 5, and the cell diameter of the foam cells formed in the extruded molded article by the foaming of the foaming agent is in the range of 50 μm to 200 μm. A weatherstrip characterized by this.

2. The weatherstrip according to claim 1, wherein the foaming agent is any one of a microcapsule, an organic foaming agent, and a supercritical fluid foaming agent.

3. An attachment base that is made of the extruded molded article and can be fitted to a door panel that is a part of an automobile body, and an elastic part that is made of a thermoplastic elastomer molded article obtained by extruding a thermoplastic elastomer composition and can be elastically contacted with a door glass provided on the door panel, The weatherstrip according to claim 1 or 2, characterized by comprising.

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