Anti-drumming compounds with high molecular weight emulsion polymers

Abstract

A description is given of the use of a polymer dispersion for producing sound deadener compositions, the polymer dispersion comprising at least one polymer obtainable by emulsion polymerization of radically polymerizable monomers, and the polymer having a weight-average molecular weight of more than 100 000, preferably of more than 100 000 to 350 000. A description is also given of corresponding sound deadener compositions which comprise the polymer dispersion, and of a method for damping oscillations or vibrations of vehicle components.

Claims

1. A sound deadener composition, comprising: (i) a dispersion comprising at least one copolymer having a weight-average molecular weight of more than 100,000 obtained by one stage emulsion copolymerization of radically copolymerizable monomers; and (i) an inorganic filler; wherein the radically copolymerizable monomers comprise: 25 to 75 wt % of at least one monomer which when polymerized as a homopolymer has a glass transition temperature of less than 0 C.; 25 to 75 wt % of at least one monomer which when polymerized as a homopolymer has a glass transition temperature of greater than 0 C. is selected from the group consisting of methyl acrylate, tert-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, acrylonitrile, methacrylonitrile, vinyl acetate, and (meth)acrylamide; and 0 to 5 wt % of at least one monomer different from the monomers (a) and (b) and having at least one acid group; wherein the at least one copolymer is not crosslinked.

2. The sound deadener composition according to claim 1, comprising; (a) 5 to 50 wt % of the dispersion, the quantity figure being based on the solids content of the polymer dispersion; (b) 40 to 80 wt % of inorganic fillers; (c) 0 to 40 wt % of organic fillers; (d) 10 to 40 wt % of water; and (e) 0 to 10 wt % of auxiliaries.

3. The sound deadener composition according to claim 2, wherein the inorganic fillers are selected from the group consisting of kaolin, chalk, barium sulfate, carbon black, graphite, talk, clay minerals, microdolomite, finely group quartz, mica, and mixtures thereof; the organic fillers when present, are selected from the group consisting of powder coating materials, polymer powders of ground solid ethylene/vinyl acetate copolymer resins, dried acrylate dispersions, polysaccharides, and mixtures thereof; and the auxiliaries are present in an amount of not less than 0.1 wt % and are selected from the group consisting of thickeners, resins, plasticizers, dispersants, cosolvents, stabilizers, wetting agents, preservatives, foam inhibitors, glass beads, plastic beads, hollow glass bodies, hollow plastics bodies, antifreeze agents, antioxidants, UV absorbers, emulsifiers, siloxanes, organically modified siloxanes, antistats, and mixtures thereof.

4. The sound deadener composition according to claim 1, further comprising an organic filler.

5. The sound deadener composition according to claim 1, wherein the at least one copolymer obtained by emulsion polymerization, comprises: (a) 25 to 75 wt % of n-butyl acrylate; (b) 24 to 75 wt % of methyl methacrylate; and (c) 0.3 to 3 wt % of at least one acid monomer selected from the group consisting of acrylic acid, methacrylic acid, and a mixture thereof.

6. The sound deadener composition according to claim 1, wherein the glass transition temperature of the polymer the at least one copolymer obtained by emulsion polymerization is in the range from 60 C. to less than or equal to +70 C.

Description

(1) The results are set out in table 1 and in FIGS. 1 and 2.

(2) FIG. 1 shows a graphical representation of the water absorption of sound deadener composition in coated form, in wt %, as a function of the weight-average molecular weight of the polymer binder. The lower line represents the water absorption after one day (24 h). The upper line represents the water absorption after 7 days.

(3) FIG. 2 shows a graphical representation of the volume expansion of sound deadener compositions in coated form, in mm, as a function of the weight-average molecular weight of the polymer binder.

(4) TABLE-US-00007 TABLE 1 Results of the performance tests: Volume Exam- WA-1 d WA-7 d Poros- Blis- expansion ple Mw .sup.1) [%] .sup.2) [%] .sup.3) ity tering [mm] A1 413 000 6 9 2 1 0.8 A2 330 000 5 8 1 1 0.4 A3 87 000 7 11 1 1 0.4 A4 50 000 8 13 1 3 0.7 A5 41 600 10 17 1 1 0.5 A6 42 700 11 20 1 1 1.0 A7 15 900 15 21 1 1 0.6 .sup.1) weight-average molecular weight of the polymeric binder .sup.2) water absorption after one day (24 h) .sup.3) water absorption after 7 days

(5) The results show that depending on the molecular weight, with polymer dispersions of the invention it is possible to achieve good water absorption (WA-1d<7%; WA-7d<11%), a good porosity, and little blistering (less than 2) of the coating, and reduced volume expansion of the coating.