JPH0516462B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an automobile side molding made of a soft PVC composition by injection molding. In this specification, the units of quantity relating to formulations are by weight unless otherwise specified. <Prior Art> Automobile side moldings serve as decoration as well as protection of the automobile body, and therefore have strict requirements regarding their appearance quality. In particular, when injection molding is performed using a soft PVC composition, it is difficult to obtain a completely smooth surface on the molded product due to variations in the amount of shrinkage in each part of the product, deformation during mold release, etc. In this case, minute irregularities become noticeable and the appearance is poor. For this reason, a large amount of heavy calcium carbonate (20 to 40 phr) is blended into the soft PVC composition to make it semi-glossy or matte so that unevenness does not appear. <Problems to be Solved by the Invention> However, when a large amount of heavy calcium carbonate is blended into a soft PVC composition, "hard eyes" due to aggregates of heavy calcium carbonate occur on the surface of the molded product. In addition, it is easy to cause a large decrease in physical properties such as tensile strength, oil resistance, and brittleness. <Means for Solving the Problems> Therefore, the present inventors have developed a method for injecting a matte side molding without incorporating heavy calcium carbonate in such a large amount as to cause hard eyes or a significant decrease in physical properties. As a result of intensive development efforts to achieve this through molding, we came up with an automotive side molding with the following configuration. In an automobile side molding injection molded with a soft PVC composition, 20 to 90 parts of 400 to 1500 partially crosslinked PVC containing 1 to 50 wt% of a THF-insoluble crosslinked part as the polymer content of the soft PVC;
It is characterized by the use of a polymer blend consisting of 400 to 1500 non-crosslinked PVC balances. <Explanation of each component> The above soft PVC composition contains (a) a polymer component, (b) a plasticizer of 20 to 80 phr, (c) a stabilizer of 1 to 8 phr, and further contains calcium carbonate, talc, clay, etc. Inorganic fillers, processing aids such as polyacrylates and polyesters, pigments, etc. are blended as necessary. In particular, it is desirable to incorporate a small amount (3 to 8 phr) of heavy calcium carbonate from the viewpoint of prevention of mold shrinkage and mixability of the composition. (a) Partially crosslinked PVC, which is one of the polymer components, is obtained by copolymerizing vinyl chloride monomer with one or more of acrylate ester, methacrylate ester, and dimethacrylate ester of polyhydric alcohol. (Refer to Tokkai No. 56-5843), vinyl chloride monomer and diallyl dipate, diallyl fumarate,
diallyl ether, triallyl cyanurate,
Products obtained by copolymerizing one or more of triallyl isocyanurate and triallyl trimellitate (see JP-A-54-80354). Further, as the non-crosslinked PVC, a normal straight polymer or vinyl acetate copolymer is used, but a straight polymer is preferable from the viewpoint of heat deformation resistance and the like. If the THF-insoluble crosslinked portion of the partially crosslinked PVC is less than 1 wt%, the surface of the side molding cannot be made matte, and if it exceeds 50 wt%, fluidity deteriorates and problems tend to occur in injection moldability.
The content of the THF-insoluble crosslinked portion is preferably 10 to 40 wt%. In addition, if the partially cross-linked PVC and non-cross-linked PVC are less than 400, it is difficult to obtain sufficient physical properties such as strength and heat resistance;
If it exceeds this, fluidity will deteriorate and problems will likely arise in injection moldability. Furthermore, the proportion of partially cross-linked PVC in the entire polymer is less than 20 parts,
In any case exceeding 90 parts, uneven luster tends to occur on the side molding surface. (b) As a plasticizer, phthalate esters such as di(2-ethylhexyl) phthalate (hereinafter abbreviated as "DOP"), dibutyl phthalate, diisodecyl phthalate, dioctyl adipate,
In addition to linear dibasic acid esters such as dioctyl sebacate, phosphate esters such as tricresyl phosphate and lorifhenyl phosphate, one type of trimellitic acid ester, polyester-based epoxy compounds, etc. Or a mixture of two or more types can be used. Here, the amount of plasticizer blended is
If it is less than 20 phr, it does not fall into the category of a soft PVC composition, and if it exceeds 80 phr, it becomes too soft and the shape retention ability required for the molding cannot be obtained. (C) Stabilizers include metal soaps such as dibasic stearates such as barium, calcium, and zinc, organotin compounds such as dialkyltin mercaptide, dialkyltin malate, dialkyltin laurate, and lead salts. They are used in combination with epoxy compounds, phosphite polyols, hindered phenols, etc. Here, if the amount of stabilizer blended is less than 1phr, the blending effect (mainly thermal stability) cannot be obtained, and 8phr
Even if the amount exceeds 100%, the blending effect will not increase much and it will be economically wasteful. After stirring and mixing the above soft PVC composition,
The material is kneaded and granulated using a twin-screw extruder or the like to obtain a material for injection. <Invention, Actions and Effects> The automobile side molding of the present invention has a polymer content of 20 to 90 parts of P400 to 1500 partially crosslinked PVC containing 1 to 10 wt% of a THF-insoluble crosslinked portion and 400 to 400 parts of partially crosslinked PVC of P400 to 1500.
By injection molding a soft PVC composition, which is a polymer blend consisting of 1,500% non-crosslinked PVC and a non-crosslinked PVC residue, it is possible to achieve a matte and hard-wearing surface with no surface irregularities, as demonstrated in the examples below. This results in good appearance quality without significant deterioration of physical properties. Although the reason for this is not necessarily clear, it is presumed that the matte surface of the product causes light to be reflected diffusely, making it difficult to notice that the surface is uneven. <Examples> Hereinafter, the present invention will be described in detail based on Examples. Mix a soft PVC composition with the formulation shown in Table 1.
Using the material obtained by kneading and granulating, the shape shown in Figure 1 (width 40 mm, length 700 mm, maximum thickness 4 mm)

[Table] Injection molding of 10 side moldings at a time (conditions: nozzle temperature 180℃, injection pressure 45Kgf/cm ² , mold temperature 50℃)
did. For each molded product, the degree of unevenness,
The gloss and the degree of occurrence of fisheye were visually judged. From the results shown in Table 1, each of the examples has a matte appearance with no visible surface irregularities and no visible stains, whereas the comparative example in which the polymer is only non-crosslinked PVC has a glossy appearance. In this case, surface irregularities can be seen (Comparative Examples 1 and 4), and when a large amount of heavy calcium carbonate is added to make the product semi-glossy or matte, hard eyes tend to occur (Comparative Examples 2, 3, 5, and 6). I understand that.

Claims (1)

[Scope of Claims] 1. A side molding for an automobile, characterized by being injection molded from a soft polyvinyl chloride (hereinafter abbreviated as "PVC") composition that satisfies the following requirements. (a) The above-mentioned soft PVC composition contains 20 to 80 phr of plasticizer and 1 to 8 phr of stabilizer based on the polymer content. (b) The polymer component contains 1 to 10% of tetrahydrofuran (hereinafter abbreviated as “THF”) insoluble crosslinked portions.
20-90 parts by weight of partially cross-linked PVC with an average degree of polymerization (hereinafter abbreviated as "") 400-1500 containing 50 wt%;
It is a polymer blend consisting of a balance of non-crosslinked PVC of P400-1500.