Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-02-26
2002-11-12
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S134000, C521S145000, C521S150000
Reexamination Certificate
active
06479559
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a chlorinated vinyl chloride resin composition for siding extrusion molding and a siding molded article using the same. More particularly, the present invention relates to a chlorinated vinyl chloride resin composition from which a siding molded article excellent in appearance, heat resistance, impact resistance and weatherability can be obtained, and a siding molded article obtained by using the same.
Vinyl chloride resins are excellent in processibility and mechanical properties and available at moderate prices. Therefore, those resins are used in a wide variety of fields including housing industry where the resin is processed into a molded article such as a window frame or a siding molded article such as a siding sheet.
Weatherability is required for siding molded articles since they are used outdoors for a long time. In view of this, siding molded articles are generally made to have a two-layered structure and the surface layer which is exposed to sunlight is made of a material having excellent weatherability to prevent discoloration and other harmful effects.
Such a two-layered structure molded article has a surface layer called “capstock” and an inner layer called “substrate”. The composite can be prepared by a method such as coextrusion. A ratio of a thickness of the capstock to that of the substrate is usually about 25/75 to 10/90.
While materials other than a vinyl chloride resin having greatly improved discoloration resistance against weather are used for the capstock, a vinyl chloride resin is generally used for the substrate.
Furthermore, required properties other than weatherability are impact resistance in a temperature range at which a siding molded article is used, and heat resistance such that the molded article is hardly deformed when surface temperature is increased by sunlight. Since these properties greatly depend upon the substrate constituting major portion of a molded article, selection of a composition for the substrate becomes important.
A vinyl chloride resin generally used for the substrate does not have sufficient impact resistance only by compounding a lubricant or a stabilizer. However, it is known that desirable impact resistance can be obtained by compounding an impact resistance modifier such as a butadiene rubber or an acrylic rubber.
Furthermore, since heat deformation temperature of a vinyl chloride resin is in a range of about 60° to 70° C., such a vinyl chloride resin is suitable for the substrate of a light tone siding molded article whose surface temperature does not exceed 70° C.
However, in the case of a siding molded article having dark color tone such as dark green, navy blue and brown, surface temperature thereof may reach at least 70° C. For this reason, a vinyl chloride resin composition having relatively low heat resistance is not suitable for the substrate of the dark-color siding molded article.
On the other hand, a chlorinated vinyl chloride resin obtained by chlorinating a vinyl chloride resin is known as a relatively inexpensive, general-purpose resin and has the characteristic that heat deformation temperature thereof is higher by 20° to 40° C. than that of a vinyl chloride resin. With putting this property into good use, the chlorinated vinyl chloride resin is used for a hot-water pipe or a heat resistant plate for industrial use. It is predicted that a dark-color siding molded article having desired heat resistance can be obtained by using a chlorinated vinyl chloride resin for a siding molded article.
By the way, impact resistance at low temperature of a chlorinated vinyl chloride resin is smaller than that of a vinyl chloride resin. Therefore, when a chlorinated vinyl chloride resin is used as a substrate, it is difficult to obtain a siding molded article having desired impact resistance. Since a siding molded article is also used as an external wall of houses, it goes without saying that impact resistance at low temperature is required.
Furthermore, it is generally said that a chlorinated vinyl chloride resin is difficult to process since it has inferior heat stability and higher melt viscosity compared to those of a vinyl chloride resin. For example, when a chlorinated vinyl chloride resin composition is extrusion-molded, die pressure and extrusion torque for an extrusion molding machine may be raised. In addition, a molded article is colored and deteriorated in appearance, burn mark being generated during extrusion molding. Thus, desirable molded articles can not be obtained in some cases.
Other various resins have similar problems, which means that a resin has not been found yet, which has properties required for a dark-color siding molded article, that is, good appearance, excellent weatherability, heat resistance, impact resistance and processibility as well as economical efficiency.
The present invention was carried out in order to solve the above problems in prior arts. An object of the present invention is to provide a chlorinated vinyl chloride resin composition for siding extrusion molding which can provide a siding molded article having excellent processibility, good appearance, excellent heat resistance, impact resistance and weatherability, and to provide a siding molded article using the same.
SUMMARY OF THE INVENTION
Intense studies were conducted to solve the above problems. As a result, the present invention has been completed based on the findings that it is possible to obtain a chlorinated vinyl chloride resin composition for siding extrusion molding which can provide a siding molded article having excellent appearance, desirable weatherability, heat resistance and impact resistance without losing processibility by preparing a siding molded article using a particular chlorinated vinyl chloride resin composition.
That is, the present invention relates to a chlorinated vinyl chloride resin composition for siding extrusion molding, comprising 100 parts by weight of a chlorinated vinyl chloride resin and 3 to 20 parts by weight of an acrylic graft rubber copolymer, wherein the acrylic graft rubber copolymer contains 30 to 90% by weight of acrylic hollow rubber particles whose average void ratio is 3 to 90% by volume in a latex state.
It is preferable that the chlorinated vinyl chloride resin composition further comprises at least two tin stabilizers.
It is also preferable that the chlorinated vinyl chloride resin composition further comprises oxidation-type modified polyethylene wax having an acid number of 0.1 to 10 mg/g measured by JIS K 5902 as a lubricant.
In addition, it is preferable that the chlorinated vinyl chloride resin composition further comprises a dark-color pigment.
The present invention also relates to a siding molded article obtained by using the above chlorinated vinyl chloride resin composition for siding extrusion molding.
Preferably, the above siding molded article has Gardner strength of at least 0.68 m·kg/mm (1.5 inch·lbs/mil) at 23° C. and HDT of at least 87.7° C. (190° F.).
DETAILED DESCRIPTION
The chlorinated vinyl chloride resin composition of the present invention comprises, as a base resin, a chlorinated vinyl chloride resin having excellent heat resistance, and an acrylic graft rubber copolymer containing 30 to 90% by weight of acrylic hollow rubber particles whose average void ratio is 3 to 90% by volume in a latex state, for improving weatherability and impact resistance of a molded article. If necessary, the chlorinated vinyl chloride resin composition of the present invention further comprises at least two kinds of tin stabilizers, at least one kind of oxidation-type modified polyethylene wax (lubricant) having an acid number of 0.1 to 10 mg/g measured by JIS K5902, and at least one kind of a dark-color pigment.
As described above, since a chlorinated vinyl chloride resin is used as a base resin, the composition has excellent heat resistance and may be also used for a substrate of a dark-color siding molded article. In addition, since an acrylic graft rubber copolymer containing 30 to 90% by weight of acryli
Okuhara Toshio
Takai Atsushi
Yamane Kazumasa
Armstrong Westerman & Hattori, LLP
Foelak Morton
Kaneka Corporation
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