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
1997-12-23
2002-02-12
Mullis, Jeffrey (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...
C525S095000, C525S096000, C525S098000, C525S099000
Reexamination Certificate
active
06346572
ABSTRACT:
The present invention relates to an impact-resistant thermoplastic molding material and a process for its preparation.
Thermoplastic molding materials based on polymers of styrene and its technical equivalents styrene/acrylonitrile or methyl meth-acrylate, are transparent and rigid but unsuitable for some applications since they are very brittle.
The usual method for obtaining impact-resistant molding materials is by toughening, the polymerization of the monomers usually being carried out in the presence of a suitable rubber,.and the rubber becoming compatible with the resulting polymer or copolymer (the matrix) as a result of grafting.
Industrially, either the polymerization of the matrix is carried out in the presence of the rubber by the mass or solution method or the required grafted rubber is prepared (generally in emulsion) and the matrix polymer is added. In the mass or solution method, multistage continuous processes are preferred (for example, DE 1 770 392; DE 4 046 718; U.S. Pat. No. 2,727,884; U.S. Pat. No. 3,903,202).
Polybutadiene rubbers and butadiene/styrene block rubbers are used for toughening styrene polymers and styrene/acrylonitrile polymers, and acrylate rubbers are also employed for styrene/ acrylonitrile polymers and methyl methacrylate polymers (cf. for example DE 2 427 960 or DE 1 260 135 and EP 244 856).
Although polybutadiene containing molding materials are tough, they are not transparent. Moreover, owing to the high double bond content, they are not very weather resistant.
The preferably used method for styrene/acrylonitrile and methyl methacrylate molding materials is free radical emulsion polymerization of the rubber phase with subsequent production of a graft shell, which serves as compatibilizer for subsequent binding to the matrix phase, and coagulation of the emulsion to give particles having an average diameter of from about 100 to 1000 nm. After drying, the particles are incorporated into the prepared matrix in a further step.
The mass/solution method for the preparation of toughened styrene polymers leads to nontransparent (opaque) molding materials which are not particularly weather resistant. The emulsion method with subsequent incorporation of the graft rubber is very expensive, and sufficient weather resistance is achieved only with acrylate rubbers or with olefin rubbers having a low double bond content (EPM, EPDM).
It is an object of the present invention to prepare, by a continuous method in existing polymerization plants, toughened molding materials which are based on styrene, styrene/acrylonitrile or methyl methacrylate with a special rubber in a simple, economical manner which does not have the abovementioned disadvantages or has them to a considerably lesser extent than in the past.
It is a further object of the present invention to provide thermoplastic molding materials based on vinylaromatic (ie. styrene) monomers, copolymers of styrene and acrylonitrile and (meth)-acrylates, which not only have substantially improved mechanical properties compared with corresponding unmodified molding materials but are also transparent.
It is a further object of the present invention to provide a process by means of which the molding materials having the above-mentioned properties can be prepared.
We have found that these and other objects are achieved, according to the invention, by mass polymerization (possibly with the addition of small amounts of a solvent) of vinylaromatic monomers (A1) or mass copolymerization of vinylaromatic monomers (A1) with polar comonomers (A2) in the presence of special butadiene-containing rubbers (b) which contain random or quasi-random blocks of styrene and butadiene and which take up occlusions of matrix material (A) during the polymerization and in this form produce the soft phase (B).
The present invention relates directly to molding materials based on
A: from 60 to 98% by weight of a hard matrix A of polymerized or copolymerized units of at least one vinylaromatic monomer or at least one vinylaromatic monomer and at least one polar comonomer and
B: from 2 to 40% by weight of a soft phase B formed from a hydrogenated or unhydrogenated block copolymer prepared by anionic polymerization and comprising a vinylaromatic monomer V and a diene D, which has at least one random or quasi-random block (V/D) of vinylaromatic monomer and diene per molecule and contains from 10 to 80% by weight, based on the soft phase B, of occlusions of matrix material (a) taken up during the polymerization,
the percentages of A and B being based on the molding material comprising A and B.
For the abovementioned composition comprising A and B, the occlusions of matrix material (a) contained in the soft phase B are not to be included.
The starting materials, the claimed molding materials and their preparation are described in more detail in the sections below and illustrated by means of examples. Hard matrix A
In general, styrene monomers are suitable as starting materials for the matrix of the polymers based on vinylaromatic monomers.
According to the invention, styrene and the conventional substituted styrenes to be regarded as technical equivalents can be used in any desired combination and mixing ratio. Styrene, alpha-methylstyrene and 4-methylstyrene or mixtures thereof are preferred. Styrene is particularly preferred.
Suitable polar comonomers A2 are polar vinyl monomers of the known structure H
2
C═CR
1
R
2
, where R
1
is hydrogen, phenyl or lower alkyl, in particular methyl or ethyl, and R
2
is carboxyl, carbo-lower-alkoxy, such as carbomethoxy, carbaryloxy, such as carbophenoxy, carboxamide, carboxy-N-lower alkyl-amide, carboxy-N-phenylamide or nitrile.
Other suitable polar comonomers A2 are maleic and fumaric anhydride and their esters, half-esters and—possibly N-lower-alkyl or aryl-substituted—imides.
Examples of suitable polar comonomers A2 are acrylonitrile, maleic anhydride, maleimide, N-phenylmaleimide, maleic and fumaric half esters and diesters, methyl acrylate, methyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, methyl acrylate, butyl acrylate, methacrylamide, acrylamide and acrylic acid.
Soft phase B
According to the invention, the soft phase (rubber phase) B is formed in the polymerization of the hard matrix A in the presence of a special block rubber, occlusions (a) of matrix material A being formed and it furthermore being possible for a certain degree of grafting to take place. The block rubber is obtained by anionic polymerization of vinylaromatic monomers (V) and diene monomers (D) according to the nonprior published German Patent Application P 44 20 952.5. This is a rubber which contains blocks of vinylaromatics and dienes having a well defined or tapered transition and contains, per molecule, at least one block (referred to below as V/D) in which V and D are randomly or quasi-randomly distributed, ie. occur in very short sequences. The block copolymers contain in total from 10 to 85, preferably from 20 to 65, % by weight of diene and from 90 to 15 or from 80 to 35% by weight of the vinylaromatics. For the novel polymer materials, they are used in an amount such that the proportion of diene is from 2 to 50, preferably from 5 to 40, % by weight.
The vinylaromatic monomers V are defined as styrene and its anionically polymerizable derivatives (alpha-methylstyrene, 2-, 3- or 4-methylstyrene, 1,1-diphenylethylene, etc.).
For the purposes of the present invention, diene monomers D are anionically polymerizable dienes, such as butadiene, isoprene, piperylene and 1-phenylbutadiene. The stated monomers may be used individually or as mixtures.
For example, block copolymers which have one of the structures below are suitable for the present invention:
(1) [V−(D/V)]
n
;
(2) [V−(D/V)]
n
−V;
(3) (D/V)−[V−(D/V)]
n
;
(4) X−[[V−(D/V)]
n
]
m+1
(5) X−[[(D/V)−V]
n
]
m+1
;
(6) X−[[V−(D/V)]
n
−V]
m+1
;
(7) X−[[(D/V)&mi
Gausepohl Hermann
Knoll Konrad
Loth Wolfgang
BASF - Aktiengesellschaft
Keil & Weinkauf
Mullis Jeffrey
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