Housings for security devices

Details Housings for security devices Housings for security devices

1999-01-22

2000-05-16

Warzel, Mark L.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

525 67, 525 84, 525 86, 174 50, 524504, C08L 5104

Patent

active

060638680

DESCRIPTION:

BRIEF SUMMARY
The invention relates to housings for security equipment, and also parts thereof. The invention relates in particular to housings with good stability and good dimensional stability, together with high scratch resistance and high yellowing resistance.
Various materials have hitherto been used for producing housings for security equipment, for example alarm systems and constituents thereof. Use is made, for example, of steel plate, which is galvanized or painted if desired. Disadvantages of steel plate are limits on shaping and susceptibility to rust.
Other materials used are ABS polymers and HIPS polymers. ABS (acrylonitrile-butadienestyrene) and HIPS (high-impact polystryene: impact-resistant polystyrene) blends have insufficient yellowing resistance in many applications, and the yellowing can be associated with a fall-off of toughness.
Another material used is polypropylene. Polypropylene tends to distort, in particular when exposed to heat. In addition, its toughness/stiffness ratio is unsatisfactory for some applications.
It is an object of the present invention to provide housings for security equipment which have high resistance to yellowing, together with great stability.
A further object of the invention is to provide housings for security equipment which are composed of parts free from weld lines.
A further object of the invention is to provide housings for security equipment which have properties superior to the housings used hitherto.
We have found that this object is achieved by using a thermoplastic molding composition differing from ABS and comprising, based on a total of 100% by weight of amounts of components A and B, and, if desired, C and/or D, polymer with a glass transition temperature of below 0.degree. C. and with a median particle size of from 50 to 1000 nm, partly crystalline polymer, fillers or mixtures of these
The thermoplastic molding compositions used according to the invention for producing the novel housings are known per se. Molding compositions which can be used according to the invention are described, for example, in DE-A-12 60 135, DE-C-19 11 882, DE-A-28 26 925, DE-A-31 49 358, DE-A-32 27 555 and DE-A-40 11 162.
In one embodiment, the molding compositions differing from ABS and used according to the invention for producing the novel housings comprise the components listed below: A and B, and, if desired, C and/or D, as defined further below. Based on amounts of components A and B, and if desired, C and/or D, which give 100% in total, they comprise weight, in particular from 25 to 50% by weight, of a particulate emulsion polymer with a glass transition temperature of below 0.degree. C. and with a median particle size of from 50 to 1000 nm, preferably from 50 to 500 nm weight, in particular from 50 to 75% by weight, of at least one amorphous or partly crystalline polymer, fillers or mixtures of these.
The invention is described in more detail below.
The molding compositions used for producing the novel housings are firstly described together with the components of which these compositions are composed.
Component A is a particulate emulsion polymer with a glass transition temperature of below 0.degree. C. and with a median particle size of from 50 to 1000 nm.
Component A is preferably a graft copolymer made from particular from 55 to 65% by weight, of a particulate graft base A1 with a glass transition temperature of below 0.degree. C., particular from 35 to 45% by weight, of a graft A2 made from these monomers, based on A2, by weight, of units of a vinylaromatic monomer, preferably of styrene, of a substituted styrene or of a (meth)acrylate or mixtures of these, in particular of styrene and/or of .alpha.-methylstyrene, and weight, of units of an ethylenically unsaturated monomer, preferably of acrylonitrile or methacrylonitrile, in particular of acrylonitrile.
The graft A2 here is composed of at least one graft shell, and the overall graft copolymer A has a median particle size of from 50 to 1000 nm.
In one embodiment of the invention, component A1 is composed of the follo

REFERENCES:
patent: 4224419 (1980-09-01), Swoboda et al.
patent: 4788253 (1988-11-01), Hambrecht et al.
patent: 4880875 (1989-11-01), Wassmuth et al.
patent: 5196480 (1993-03-01), Seitz et al.

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