Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-04-26
2003-07-08
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S356000
Reexamination Certificate
active
06590041
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a vinyl chloride resin, a chlorinated vinyl chloride resin and a method of producing the same, a chlorinated vinyl chloride resin pipe, a chlorinated vinyl chloride resin joint and a chlorinated vinyl chloride resin plate.
BACKGROUND ART
Vinyl chloride resins (hereinafter sometimes referred to also as “PVC” or “PVC resins”) are used in various fields as materials having good mechanical strength, weathering resistance and chemical resistance. Since, however, PVC resins have the drawback of being inferior in shock resistance, various methods have been proposed to improve their shock resistance. Thus, for example, addition of a copolymer having rubber-like properties and/or high-level addition of an inorganic material, a metal powder or the like has been practiced.
Japanese Kokoku Publication Sho-44-453 discloses a method comprising blending, with PVC resins, a methyl methacrylate-butadiene-styrene copolymer (MBS copolymer) as a dispersoid. Japanese Kokai Publication Hei-02-20545 discloses a method comprising blending, with PVC resins, a chlorinated polyethylene (CPE resin) as a dispersoid.
However, when an MBS copolymer or a CPE resin is blended with PVC resins, the problem of lowered moldability arises, although the shock resistance is improved to a certain extent. Further, such a method comprising blending a copolymer having rubber-like properties with PVC resins pays attention only to the dispersoid but not to the PVC resins themselves, which are dispersion media, and accordingly the shock resistance improving effect is limited.
Furthermore, in many cases, loading materials, fillers, reinforcements and the like are incorporated in PVC resins for providing them with mechanical strength and functions. Therefore, PVC resins highly capable of dispersing other kinds of materials therein and allowing high level addition thereof and having good gelation properties are demanded. Further, since PVC resins excellent in gelation properties are generally excellent in high-speed moldability, PVC resins having good gelation properties as well are desired.
For improving such gelation properties and attaining high level loadability and dispersibility of materials of other kinds, it is necessary that the PVC resins be readily disintegrable and have micropores within resin particles with a high void content.
On the other hand, PVC resins are inferior in heat resistance. Therefore, chlorinated vinyl chloride resins (hereinafter referred to also as “CPVC” or “CPVC resins”) have been developed which are produced by chlorinating PVC resins and thus improved in heat resistance.
While PVC resins have a low thermal deformation temperature and the upper limit temperature allowing their practical use is around 60 to 70° C., hence they cannot be used in contact with hot water, CPVC resins have a thermal deformation temperature higher by 20 to 40° C. as compared with PVC resins, so that they can be used in contact with hot water and are thus favorably used as materials of heat-resistant pipes and heat-resistant joints, typically for hot water supply, or of heat-resistant resin material plates for producing tanks or containers, for instance. Through the use of CPVC, the problem of rusting due to corrosion so far encountered with the conventional metal pipes, metal plates and the like has been liquidated.
However, since CPVC resins have a high thermal deformation temperature, a high temperature and great shearing force are required for effecting gelation in the step of molding/fabrication, tending to cause degradation and discoloration of the resins. CPVC resins thus have a narrow margin of moldability and they are often molded into products in an insufficient gelation state and, on such occasions, the products can hardly be said to have fully inherited the performance characteristics intrinsic in the material resins.
In addition to such improvement requirement concerning gelation properties, a higher level of heat resistance, too, is now required. In the case of heat-resistant pipes, heat-resistant joints and reservoirs for holding chemical liquids, for instance, they are liable to expand to the extent of undergoing deformation and fracture when high-temperature steam at 100° C. or higher is generated as the result of, for instance, a failure in the operation of a safety device or upon introduction of a chemical liquid heated to 100° C. or above. For passing a liquid or gas at 100° C. or above through such heat-resistant pipes or heat-resistant joints or introducing a chemical liquid at 100° C. or above into such chemical liquid reservoirs, the pipes and joints for hot water supply are required to have still higher levels of heat resistance and chemical resistance as compared with the conventional pipes and joints for hot water supply. They, in particular, are required to have high shock resistance such that they may withstand water hammer shocks. For that purpose, it is necessary that the gelation of CPVC resins be sufficient.
For solving such problems, Japanese Kokai Publication Sho-49-6080, for instance, discloses a method comprising chlorinating a PVC resin in the form of aggregates consisting of primary particles about 1 &mgr;m in size as resulting from the use of a suspension stabilizer composed of an ionic emulsifier, a water-soluble metal salt and a water-soluble macromolecular dispersant (i.e. proposal for improving resin particles). This method indeed improves the gelation properties in the step of molding/fabrication but, the improvement is not yet satisfactory. In addition, a problem arises: a large amount of scale is formed in the step of polymerization and sticks to the polymerizer wall surface to thereby lessen the heat removing effect, hence work is required to remove said scale.
Japanese Kkai Publication Hei-04-81446 discloses a method of attaining a high thermal deformation temperature which comprises using a resin composition having a specific chlorine content and a shock resistance enhancer. However, the heat resistance attainable is still below the level intended to reach by us.
Japanese Kokai Publication Hei-05-132602 discloses a method of attaining high heat resistance which comprises blending a CPVC resin with a PVC resin so as to obtain a viscosity in a specific range (proposal-for improvement by resin blending) However, this method is only expected to bring about an improvement in heat resistance by about 3 to 4° C. in terms of Vicat value as well as a certain extent of gelling performance improvement owing to the improvement in melt viscosity. The method can never satisfactorily attain the high levels of heat resistance and gelation properties which are aimed at by us.
Japanese Kokai Publication Hei-06-128320 discloses a method of chlorinating PVC-resins which comprises two steps (two-step chlorination method). This method is intended to produce highly heat-resistant CPVC resins by increasing the chlorine content to 70 to 75% by weight (proposal for improvement by high level chlorination). However, while this method can be expected to afford high heat resistance according to the chlorine content, no means is disclosed for preventing the gelation properties from predictably worsening as a result of high level chlorination and, accordingly, the method cannot provide practical levels of high heat resistance and gelation properties.
Japanese Kohyo Publication Sho-57-501285 discloses a method of producing highly heat-resistant CPVC resins by effecting the chlorination reaction under ultraviolet irradiation which method employing a chlorine pressure within the range of 25 to 100 psi (1.75 to 7 kg/cm
2
) and using resin particles restricted in porosity to 0.1 to 0.7 cc/g and in surface area to 0.7 to 2 m
2
/g. However, only the chlorination pressure is considered as the condition for attaining high heat resistance in this chlorination reaction. The ranges given for the porosity and surface area of resin particles are too broad and no preferred ranges are shown therefor. The CPVC resins obtained are thus mostly low in heat resistance. Fu
Asahina Ken-ichi
Eguchi Yoshihiko
Gotoh Yuhki
Iijima Ryo
Inoue Hideki
Lipman Bernard
Sekisui Chemical Co. Ltd.
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