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
2000-10-31
2002-06-18
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S222000, C525S232000, C525S239000, C525S241000
Reexamination Certificate
active
06407173
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a synthetic resin having improved powder characteristics, and more particularly to an MBS resin useful as an impact modifier for vinyl chloride resins.
BACKGROUND ART
Vinyl chloride resins are thermoplastic resins which are inexpensive and excellent in transparency, and are general purpose type resins which are widely used for wrapping for the property of transparency. Vinyl chloride resins are also used in building materials such as side wall, window frame and sash, and hard products such as pipe and joint for the good properties of mechanical strength, weatherability and chemical resistance. However, in many cases of using vinyl chloride resins for these purposes, vinyl chloride resins are not sufficient in impact resistance and, therefore, a methyl methacrylate/butadiene/styrene copolymer (MBS resin) has been generally incorporated as an impact modifier into vinyl chloride resins in order to impart an impact strength thereto. Particularly, in recent years, it is more strongly demanded than before that the MBS resin for vinyl chloride resins can highly improve the impact strength.
As a general method to further improve the impact strength of vinyl chloride resins with MBS resins, it has been conventionally adopted to increase the proportion of a rubber to be used in the MBS resins, namely to increase the proportion of butadiene (Bd). However, if the content of Bd units in the MBS resins is increased too much, the powder characteristics of MBS resins are markedly deteriorated. For example, since the granulation property is lowered, a massive resin is only obtained when powdering the resin from a latex and, therefore, it is difficult to make the product by a plant. Also, there arises a so-called blocking problem that since blocking occurs during storage or transfer of the powdery product, it is difficult to take out the MBS resin from silo, container or bag, or since bridging occurs in the vicinity of a discharge port when discharging from a hopper, spontaneous discharge is not possible.
Improvement in such powder characteristics of MBS resins is also strongly demanded in recent years, and the powder characteristics are now one of important characteristics of MBS resins. Various proposals for improving the powder characteristics have hitherto been reported. For example, Japanese Patent Publication Kokai No. 57-59929 discloses a method for improving the blocking resistance by coagulating a latex of a graft copolymer in a gas phase. Japanese Patent Publication Kokai No. 7-3106 discloses a method for improving the blocking resistance by adding a specific polymer to MBS resins. However, in case of MBS resins having a high Bd content, these methods still cannot achieve the powder characteristics demanded.
As mentioned above, it is essential for imparting a higher impact resistance to vinyl chloride resins to use a larger amount of Bd. Also, in case that vinyl chloride resins are used for the purposes which require a transparency, it is also necessary for maintain the transparency to fairly strictly match the refraction index of MBS resin with that of a vinyl chloride resin and, therefore, the composition of components constituting the MBS resin is restricted. Like this, due to the contradictory factors and restriction in constituting components, it is very difficult to improve the powder characteristics of MBS resins having a high Bd content to be incorporated into vinyl chloride resins intended to use for purposes which require a transparency.
It is an object of the present invention to provide, under circumstances as mentioned above, an MBS resin used for vinyl chloride resins having a high transparency, which has a high Bd content but has an improved powder characteristics.
A further object of the present invention is to provide an impact modifier for vinyl chloride resins, which is improved in granulation property and blocking resistance and which can impart a high impact resistance to the vinyl chloride resins.
Another object of the present invention is to provide a vinyl chloride resin composition having excellent transparency and impact resistance which comprises a vinyl chloride resin and an MBS resin type impact modifier.
DISCLOSURE OF INVENTION
The present invention provides a resin having an improved powder characteristics and useful as an impact modifier for vinyl chloride resins, which comprises an MBS resin satisfying the following relational equations (1) and (2):
−1.5
x+
140
≦y≦−
1.65
x+
180 (1)
55
≦x≦
70 (2)
wherein x is a butadiene content (% by weight) in the MBS resin, and y is a Vicat softening point (°C.) of the MBS resin, and 0.1 to 10 parts by weight of a hard polymer per 100 parts by weight of said MBS resin, and which is obtained by coagulating a latex of said MBS resin, adding said hard polymer in the state of latex or coagulated slurry to the resulting coagulated slurry of MBS resin, and recovering the powder from the resulting mixture.
As the hard polymer is preferably used a copolymer of methyl methacrylate, an aromatic vinyl monomer, a crosslinking agent and 0 to 30% by weight of other copolymerizable monomer.
BEST MODE FOR CARRYING OUT THE INVENTION
The MBS resins used in the present invention are prepared by graft-polymerizing a monomer component comprising an alkyl methacrylate, preferably methyl methacrylate, an aromatic vinyl compound such as styrene and optionally other vinyl monomers copolymerizable therewith such as methyl acrylate, ethyl acrylate, butyl acrylate and acrylonitrile onto a crosslinked or non-crosslinked butadiene-based rubber such as polybutadiene (PBd), styrene-butadiene rubber (SBR) or acrylonitrile-butadiene rubber (NBR) in a conventional manner.
The content x of Bd (weight percentage of Bd monomer units) included in MBS resins is from 55 to 70% by weight, preferably from 60 to 68% by weight. If the Bd content is less than 55% by weight, the impact resistance of molded articles prepared by mixing with a vinyl chloride resin and molding the resulting mixture is insufficient. If the Bd content exceeds 70% by weight, the amount of Bd is too much, so not only a good powder is not obtained due to formation of a mass in the step of powdering the MBS resin from a latex obtained as a result of polymerization, but also the transparency of vinyl chloride resin molded articles cannot be retained because it becomes difficult to match the refraction index of the MBS resin with that of a vinyl chloride resin. MBS resins having a Bd content of 60 to 68% by weight are preferable since they can provide vinyl chloride resins with a sufficient impact strength and, moreover, a powder having good powder characteristics is obtained.
The blocking resistance which is a measure of the powder characteristics has a close relationship to the Vicat softening point (°C.) of MBS resin. The Vicat softening point is measured under a load of 1 kg according to JIS K 7206. In general, the higher the softening point, the better the granulation property and the blocking resistance. The range of the Vicat softening point (y) of MBS resin used in the present invention is represented by the following equation:
−1.5
x+
140
≦y≦−
1.65
x+
180,
preferably,
−1.2
x+
128
≦y≦−
1.65
x+
180
wherein x is the Bd content (% by weight) of MBS resin.
If the Vicat softening point (y) is less than “−1.5x+140”, the granulation property is bad since the softening point becomes too low with respect to the Bd content. From the viewpoint of better granulation property, it is preferable that the Vicat softening point is not less than “−1.2x+128”. If the Vicat softening point is more than “−1.65+180”, the impact resistance-improving effect of MBS resin is lowered.
In general, the Vicat softening point is mainly determined by the kinds and amounts of monomers which constitute MBS resin and is closely related with the glass transition temperatures of the respective components, although it is also affe
Takaki Akira
Uemura Akira
Yauchi Shinichi
Yoshioka Masahito
Armstrong Westerman & Hattori, LLP
Kaneka Corporation
Nutter Nathan M.
LandOfFree
Impact modifier resin for vinyl chloride resins improved in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Impact modifier resin for vinyl chloride resins improved in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Impact modifier resin for vinyl chloride resins improved in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2893373