Thermally hardenable preparations

Abstract

The subject matter of the present application is thermally-expandable preparations, containing (a) at least one peroxide-crosslinkable polymer, (b) at least one low-molecular, multifunctional acrylate, (c) at least one peroxide and (d) at least two different chemical propellants, the mass ratio of the at least one peroxide to the at least one low-molecular, multifunctional acrylate being at least 1:3.

Claims

1. A thermally expandable preparation, comprising (a) at least one peroxide-crosslinkable polymer, (b) at least one low molecular weight multifunctional acrylate, (c) at least one peroxide, and (d) at least two chemical blowing agents, wherein the thermally expandable preparation has a mass ratio of the at least one peroxide to the at least one low molecular weight multifunctional acrylate that is at least 1:3; (d) comprises at least one sulfonic acid hydrazide and azodicarbonamide and the thermally expandable preparation has a mass ratio of sulfonic acid hydrazide to azodicarbonamide that is at least 3:1; and the at least one peroxide-crosslinkable polymer is present as one or more ethylene-vinyl acetate copolymers, in the absence of functionalized ethylene-vinyl acetate copolymers furnished with anhydride groups; the thermally curable preparations being essentially free from additional peroxide-crosslinkable polymers, apart from the one or more ethylene-vinyl acetate copolymers.

2. The thermally expandable preparation according to claim 1, wherein the one or more ethylene-vinyl acetate copolymers comprises an ethylene-vinyl acetate copolymer with a vinyl acetate content of 9 to 30 wt. %.

3. The thermally expandable preparation according to claim 1, wherein the one or more ethylene-vinyl acetate copolymers comprises an ethylene-vinyl acetate copolymer having a melt flow index of 0.3 to 400 g/10 min.

4. The thermally expandable preparation according to claim 1, wherein the low molecular weight multifunctional acrylate is selected from triethylene glycol dimethacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate (TMPTA) and trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (TMM), tetramethylolmethane tetraacrylate (TMMT), pentaerythritol trimethacrylate, di(trimethylolpropane) tetraacrylate (TMPA) and pentaerythritol tetraacrylate.

5. The thermally expandable preparation according to claim 1, wherein the at least one peroxide is deposited onto a solid inert carrier.

6. The thermally expandable preparation according to claim 1, further comprising an activator for the azodicarbonamide.

7. A thermally expandable preparation, comprising: (a) at least one peroxide-crosslinkable polymer, (b) at least one low molecular weight multifunctional acrylate, (c) at least one peroxide, and (d) at least two chemical blowing agents, wherein the at least one peroxide-crosslinkable polymer comprises an ethylene-vinyl acetate copolymer with a vinyl acetate content of 9 to 30 wt. %; and the thermally expandable preparation has a mass ratio of the at least one peroxide to the at least one low molecular weight multifunctional acrylate that is greater than 0.333.

8. A thermally expandable preparation, comprising: (a) at least 66 wt. % of at least one peroxide-crosslinkable polymer selected from the group consisting of ethylene-vinyl acetate copolymers, ethylene-butyl acrylate copolymers, ethylene-propylene-diene copolymers, styrene-butadiene block copolymers, styrene-isoprene block copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers and ethylene-(meth)acrylic acid copolymers in the absence of functionalized copolymer furnished with anhydride groups; (b) at least one low molecular weight multifunctional acrylate, (c) at least one peroxide, (d) at least two chemical blowing agents comprising at least one sulfonic acid hydrazide present in an amount of 5.0 to 12.5 wt. % and an azodicarbonamide present in an amount of 0.5 to 3.5 wt. %, and (e) 5 to 10 wt. % of at least one filler, wherein the thermally expandable preparation has a mass ratio of the at least one peroxide to the at least one low molecular weight multifunctional acrylate that is at least 1.3.

Description

EXAMPLES

(1) 1 Production of the Formulations

(2) 1.1 Production of the Masterbatches

(3) Various masterbatches were produced with colorant, talc, zinc ditoluene sulfinate, trimethylolpropane trimethacrylate, dicumyl peroxide, di(tert-butylperoxyisopropyl)benzene, EVA, LDPE, bis-(3,3-bis-(4-hydroxy-3-tert. butylphenyl)butanoic acid glycol ester, diphenyloxide-4,4-disulfohydrazide and azodicarbonamide in the quantities listed in Table 1. For this the components were mixed together, fed at 70-90 C. into a continuous twin screw extruder and then extruded and pelletized.

(4) 1.2 Production of the Thermally Expansible Preparations

(5) In order to produce the thermally expansible preparations according to the invention, the various masterbatches, each with the quantities listed in Table 1 of additional ethylene-vinyl acetate copolymer, were mixed at 70 to 110 C. in a twin screw injection molding machine, injected in various shapes of plaque (20 cm20 cm, thickness 2-6 mm) and cooled down to room temperature.

(6) 2 Determination of the Expansion

(7) In order to determine the expansion, test specimens (40 mm40 mm4 mm) were cut out of prepared plaques and placed in a circulating air oven that was heated to the temperature listed in Table 1 (heat-up time ca. 7 to 10 min) and the test specimens were then left at this temperature for the length of time cited in Table 1. The expansion at 180 C. corresponds here to the ideal conditions that are obtained in the context of the curing step in automobile construction. The expansion at 150 C. simulates the conditions of under-cure, the expansion at 220 C. the conditions of over-cure.

(8) The degree of expansion was measured by means of the water displacement method according to the Formula

(9) $\mathrm{Expansion}=\frac{\left(m2-m1\right)}{m1}100$
m1=mass of the test specimen in deionized water in the original state
m2=mass of the test specimen in deionized water after curing.
3 Determinafion of the Adhesion on Various Types of Steel

(10) In another test series the adhesion of the obtained expanded compositions on various types of steel was determined. Three samples of each of the following steels were used and the mean value of the results determined:

(11) HDG: hot dipped galvanized steel

(12) EGS: electro galvanized steel

(13) CRS: cold rolled steel

(14) KTL: electrocoated steel

(15) A strip (150 mm20 mm2 mm) from the injection molded plaque was laid in the middle of an oiled metal sheet (250 mm100 mm0.8 mm); oiled with Multidraw PL 61; manufacturer Zeller & Gmelin) and fixed by screwing through the metal sheet and material. At a distance of 6 mm from the base metal sheet, a second cover sheet (250 mm30 mm0.8 mm) was mounted by means of fixing screws directly above the material and the assembly was stored for at least one hour at 23 C. to condition it prior to curing. The test specimens were then heated in a circulating air oven for the times and temperatures shown in Table 1; the product when heated expanded and filled the gap between base and cover sheet (sandwich assembly). At the conclusion of the heating the test sheet was stored at 23 C. for at least 4 hours. The adhesion was tested at an angle of 180 by loosening the screws and removing the cover sheet.

(16) 4 Formulation and Measurement Results

(17) 4.1 Tabular Overview

(18) Unless otherwise stated, the quantities are understood to be in weight percent.

(19) TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 VV1 VV2 Colorant, black 0.2 0.2 0.2 0.3 0.5 0.2 Talc 6.6 7.2 5.8 9.8 15.8 3.3 6.6 Unicell TM 0.6 0.6 0.6 0.8 1.4 0.4 0.6 Sartomer SR 350 0.8 0.6 1.6 0.8 1.2 1.6 1.6 Perkadox 14-40 B-PD 1.6 1.2 1.6 1.6 2.6 1 0.8 Elvax 460A 7.8 7.8 7.8 10.6 17.2 7.8 Icorene MP 650-35 5.0 Hostanox 03 PWD 0.2 0.2 0.2 0.3 0.4 0.1 0.2 Unicell OH 5.6 5.6 5.6 7.7 12.4 1 5.6 Unicell D200A 1.6 1.6 1.6 2.1 3.5 3.6 1.6 Elvax 460A 75 75 75 66 45 84 75 SUM 100 100 100 100 100 100 100 Expansion at 15 min @ >500 >500 >500 >500 >500 <200 <500 150 C. [%] Adhesion to 100% 100% 100% 100% 100% 0% 80% HDG/EGS/CRS/KTL at cohesive cohesive cohesive cohesive cohesive cohesive cohesive 15 min @ 150 C. (oiled with 3 g/m2) Expansion bei 10 min @ >650 >600 >600 >700 >800 >500 <650 180 C. [%] Adhesion to 100% 100% 100% 100% 100% 80% 100% HDG/EGS/CRS/KTL at cohesive cohesive cohesive cohesive cohesive cohesive cohesive 10 min @ 180 C. (oiled with 3 g/m2) Expansion at 40 min @ >700 >700 >700 >800 >1000 <500 >700 220 C. [%] Adhesion to 100% 100% 100% 100% 100% 80% 100% HDG/EGS/CRS/KTL at cohesive cohesive cohesive cohesive cohesive cohesive cohesive 40 min @ 220 C. (oiled with 3 g/m2)
4.2 Index of the Utilised Commercial Products

(20) TABLE-US-00002 Elvax 460A ethylene-vinyl acetate copolymer, (ca. 18 wt % vinyl acetate content in the copolymer, melt flow index 2.5 g/10 min at 190 C. and a weight of 2.16 kg) (DuPont) Hostanox ethylene glycol-bis[3,3-bis(3-tert-butyl-4- 03 PWD hydroxyphenyl)-butanoate] (Clariant) Icorene LDPE, powder, melt temperature 90-120 C., MP 650-35 colorless, Perkadox di-(tert-butylperoxyisopropyl)benzene on a calcium 14-40 B-PD carbonate-silica carrier, ca. 40 wt % active substance content (Akzo Nobel) Sartomer trimethylolpropane trimethacrylate (Sartomer) SR 350 Unicell D200A azodiacarbonamide (Tramaco) Unicell OH diphenyloxide-4,4-disulfohydrazide (OBSH) (active substance content more than 90%) (Fernz Speciality Chemicals) Unicell TM zinc di-toluene sulfinate (Tramaco)
4.3 Expression of Results

(21) The exact compositions of the various formulations as well as the results of the determination of the expansion behavior and the adhesion behavior under different conditions were summarized in Table 1.

(22) 4.3.1 Comparison with Comparative Test VV1

(23) Whereas 100% of the inventive preparations 1 to 5 exhibited an advantageous cohesive fracture behavior under the test conditions, the comparative formulation VV showed a significantly higher number of adhesive fractures (up to 0% cohesive in the case of under-cure conditions). The adhesion of the comparative formulation on oiled steel is consequently significantly worse than the adhesion of the inventive formulations under the same conditions.

(24) In addition it can be seen from the measured expansion degrees that the inventive preparations continued to expand when the curing temperature was increased. Even with strong over-cure conditions (heating to 220 C. for 40 minutes), these preparations did not slump, but continued to expand. In contrast, the comparative formulation from the prior art showed an expansion maximum when cured at 180 C. and then began to shrink in a disadvantageous manner.

(25) 4.3.2 Comparison with Comparative Test VV2

(26) a) Expansion

(27) In the under-cure range (expansion at a temperature of ca. 150 C.) the comparative example 2 exhibited a significantly lower expansion than the inventive formulations. This effect also still occurred for an expansion at ca. 180 C.

(28) b) Adhesion

(29) In the determination of the adhesion to oiled metal sheets the comparative formulation VV2 showed in the under-cure conditions only 80% cohesive fracture behavior and thus showed a significantly poorer adhesion under these conditions than the inventive formulations.

(30) c) Filling Out Narrow Cavities

(31) For the purposes of comparison the inventive formulation 1 and the comparative formulation VV2 were again processed into plaques (200 mm200 mm4 mm). Strips (80 mm30 mm4 mm) were cut out of each plaque and laid in 3 layers on top of one another in a (symmetrical) metal pipe with a depth of 10 cm and a trapezoidal cross section (90 mm/78 mm45 mm). The metal pipes filled with the strips were then each cured for 10 minutes at 180 C. (object temperature).

(32) This test showed that the comparative formulation 2 did not completely fill the cavity (only 75-80% of the volume of the cavity was filled); consequently the cavity was not sealed. In contrast, the inventive composition of example 1 completely filled up the cavity and adequately sealed up the available volume.

(33) d) Summary

(34) It has therefore been demonstrated that the inventive formulation 1 (mass ratio of the at least one peroxide to the at least one low molecular weight multifunctional acrylate was 0.8 (greater than 0.333)) is superior to the formulation of the comparative example 2 (mass ratio of the at least one peroxide to the at least one low molecular weight multifunctional acrylate was 0.2 (less than 0.333)) both in regard to the expansion rate as well as in regard to the fracture behavior. Also, in regard to the sealing of three-dimensional cavities, the inventive formulation surprisingly proved to be significantly superior.