PRE-CURED PRODUCT FOR THERMALY EXPANDABLE COMPOSITIONS

Abstract

A product, especially a master-batch for producing thermally expandable compositions, is obtainable or obtained by reacting, preferably by extruding, a mixture including: (a) at least one polymer P, cross-linkable by peroxide, and (b) at least one coagent, especially an acrylate A, and (c) at least one peroxide PE, wherein the mixture is reacted such that the product has an average melt flow index (MFI) of between 0.1 and 8 g/10 min.

Claims

1. A product obtainable or obtained by reacting, a mixture comprising: (a) at least one polymer P, cross-linkable by peroxide, and (b) at least one coagent, and (c) at least one peroxide PE, wherein the mixture is reacted such that the product has an average melt flow index (MFI) of between 0.1 and 8 g/10 min.

2. The product according to claim 1, wherein the at least one polymer P comprises more than 70 wt. % of ethylene-vinyl acetate (EVA), based on the total amount of the Polymer P.

3. The product according to claim 1, wherein the at least coagent comprises a polyfunctional acrylate A with an acrylate functionality of at least 2 or 3, in an amount of more than 70 wt.-%, based on the total amount of the Acrylate A.

4. The product according to claim 1 wherein in the obtained product, based on the initial amount of peroxide PE initially present in the mixture for obtaining product PR, a content of the at least one peroxide PE in unreacted state is between 0 and 5 wt. %.

5. The product according to claim 1 wherein, in the unreacted mixture, a weight ratio of the at least one polymer P to the at least one peroxide PE is between 1 and 500.

6. The product according to claim 1 wherein, based on the total weight of the unreacted mixture, the mixture for obtaining the product PR comprises between 0.05-10 wt. %, of the at least one peroxide PE.

7. The product according to claim 1 wherein the reaction for obtaining the product PR takes place essentially in the absence of a blowing agent.

8. A thermally expandable composition comprising a product as defined in claim 1 and (d) at least one blowing agent.

9. The thermally expandable composition according to claim 8 wherein the blowing agent is selected from azo compounds, hydrazides, nitroso compounds, carbamates, and/or carbazides.

10. The thermally expandable composition according to claim 8 wherein an amount of the blowing agent is between 2 and 15 wt.-%, based on the total weight of the thermally expandable composition.

11. A baffle and/or reinforcement element for open and/or hollow structures, wherein the element comprises a thermally expandable composition according to claim 8.

12. A method for obtaining a product, comprising the step: i) reacting a mixture comprising: (a) at least one polymer P, cross-linkable by peroxide, and (b) at least one coagent, and (c) at least one peroxide PE, wherein the mixture is reacted such that the product has an average melt flow index (MFI) of between 0.1 and 8 g/10 min.

13. The method for producing a thermally expandable composition comprising the steps of: i) obtaining a product PR according to claim 12 ii) mixing the product PR obtained in step i) with at least one blowing agent and optionally extruding the mixture.

14. The method according to claim 13, wherein step i) is effected at a higher temperature than step ii).

15. The method for producing a thermally expanded composition comprising the steps of: i) obtaining a product PR according to claim 13 ii) obtaining a thermally expandable composition by mixing the product PR with at least one blowing agent and optionally extruding the mixture iii) expanding the thermally expandable composition obtained in step ii) by a heat treatment.

16. A method comprising producing a thermally expandable composition with a product according to claim 1 as a precursor and/or producing a baffle and/or a reinforcer, whereby the baffle and/or a reinforcer is designed for baffling, sealing and/or reinforcing a cavity or hollow structure of a land-, water-, or air-vehicle, and/or a cavity of a building such that the transmission of noise, vibrations, humidity, and/or heat is reduced, and/or the object surrounding the cavity is mechanically strengthened.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0154] FIG. 1 shows the storage modulus (G′) and the loss modulus (G″) of a sample made from a conventional thermally expandable composition as a function of temperature.

[0155] FIG. 2 shows the storage modulus (G′) and the loss modulus (G″) of a sample made from an inventive thermally expandable composition as a function of temperature.

EXAMPLES

1. Formulation of Master-Batches and Thermally Expandable Compositions

1.1 Ingredients

[0156] Details on the ingredients used in the examples are listed in the following Table 1:

TABLE-US-00001 TABLE 1 Details on the ingredients and their trade names used in the inventive and non-inventive example compositions in this document. Ingredient Description Properties or trade name Polymer Ethylene-vinyl acetate (EVA) EVA with 18 wt.-% vinyl P1 copolymer resin acetate monomer and a melt flow index (MFI) of 150 g/10 min (ATSM D1238) Polymer Ethylene-vinyl acetate (EVA) EVA with 28 wt.-% vinyl P2 copolymer resin acetate monomer and a MFI of 6 g/10 min (ATSM D1238) Adhesion Ethylene-glycidyl MFI of 5 g/10 min (ASTM promoter methacrylate copolymer (8 D1238) (AP) wt.-% glycidyl methacrylate) Tackifier C5-C9-Hydrocarbon resin Mn 1100 g/mol, Mw 2000 g/mol, Dispersion Polyethylene wax Melting point 118° C. (ASTM aid D3954) Stabilizer Stabilizer Irganox 1010 Filler Calcium carbonate ZnO Zinc oxide, Activator Sigma Aldrich, Switzerland ACDA Azodicarbonamide Tramaco, Germany PE Peroxide, Di-(2-tert.-butyl- Pergan, Germany peroxyisopropyl)-benzene (40 wt.-%) on calcium carbonate and silica Acrylate Dipentaerythritol Sartomer Arkema (A) pentaacrylate

1.2 Master-Batches

[0157] 6 examples of inventive master-batches (product PR) (E1 to E6) and 3 non-inventive reference master-batches (R1 to R3) were prepared according to the following procedure: The ingredients were mixed in a dual screw extruder (Berstorff ZE-25R twin screw extruder; 200 rpm) at a temperature of 35° C. in the first section of the mixing zone, at a temperature of 185° C. in the middle section of mixing zone and at a temperature of 170° C. at the end section of the mixing zone. Subsequently, the so obtained products were extruded with a throughput of 10 kg/hour.

[0158] The individual compositions of the master-batches in wt.-%, based on the total weight of the respective master-batch as well as their melt flow indexes (MFI; measured according to standard ASTM D1238-13; test method: T=190° C., m=2.16 kg; procedure A, condition E) and peroxide content, are listed in tables 2 and 3.

TABLE-US-00002 TABLE 2 Compositions of inventive master-batches produced. E1 E2 E3 E4 E5 E6 Ingredients P1 [wt.-%] 44.18 44.14 44.48 44.28 44.45 44.62 P2 [wt.-%] 25.77 25.75 25.94 25.82 25.92 26.02 AP [wt.-%] 20.52 20.5 20.66 20.57 20.65 20.73 A [wt.-%] 0.37 0.75 0.05 0.75 0.41 0.05 Dispersion 7.96 7.95 8.01 7.98 8.01 8.04 aid [wt.-%] PE [wt.-%] 1.20 0.91 0.87 0.60 0.57 0.54 TOTAL 100.00 100.00 100.00 100.00 100.00 100.00 Proportions A/PE 0.31 0.83 0.06 1.24 0.71 0.09 P/A (P = 246 121 1822 121 224 1827 P1 + P2) P/PE 75 100 105 150 159 168 Product properties MFI [g/10 min] 0.34 0.35 1.21 2.85 2.25 4.85 Peroxide >99.9 >99.9 >99.9 >99.9 >99.9 >99.9 converted [% of initially provided peroxide]

TABLE-US-00003 TABLE 3 Compositions of non-inventive master-batches produced. R1 R2 R3 Ingredients P1 [wt.-%] 44.67 44.80 44.51 P2 [wt.-%] 26.05 26.12 25.96 AP [wt.-%] 20.75 20.81 20.67 A [wt.-%] 0.38 0.10 0.72 Dispersion aid [wt.-%] 8.08 8.07 8.02 PE [wt.-%] 0.10 0.10 0.12 TOTAL 100.00 100.00 100.00 Proportions A/PE 3.75 0.95 5.95 P/A (P = P1 + P2) 244 966 128 P/PE 915 917 759 Product properties MFI [g/10 min] 12.44 21.44 8.92 Peroxide converted >99.9 >99.9 >99.9 [% of initially provided peroxide]

[0159] From the results in tables 2 and 3 it is evident that the proportion of PE or the ratio of P/PE, respectively, is related to the MFI. The more PE or the lower the ratio of P/PE, the lower the MFI. A lower MFI is indicative for a higher degree of cross-linking in the product.

[0160] For instance, example 2 with 0.91 wt.-% PE, 0.75 wt.-% acrylate (A) and P/PE=100 has an MFI of 0.35 whereas example 4 with the same proportion of acrylate, 0.6 wt.-% PE, and P/PE=150 has an MFI of 2.85. Likewise, example 3 with 0.87 wt.-% PE, 0.05 wt.-% acrylate (A) and P/PE=105 has an MFI of 1.21 whereas example 6 with the same proportion of acrylate, 0.54 wt.-% PE and P/PE=168 has an MFI of 4.85.

[0161] Moreover, it is evident that the proportion of acrylate (A) or the ratio of P/A, respectively, is related to the MFI. The higher the proportion of acrylate or the lower the ratio of P/A, the lower the MFI. For instance, example 7 with 0.38 wt.-% acrylate and P/A=244 the MFI is 12.44 whereas example 8, which has the same proportion of PE as example 7, 0.1 wt.-% of acrylate and P/A=966, the MFI is 21.44. A similar situation can be recognized when comparing example 2 versus example 3 or example 5 versus example 6.

1.3 Conventional Thermally Expandable Composition

[0162] A non-inventive thermally expandable reference composition (C-R1) was prepared based in the ingredients given in table 4 and the procedure described below. The melt flow index of this composition was determined according to a test similar to the method defined in standard ASTM D1238-13. However, in order to prevent expansion of the composition, the melt flow index was determined at a temperature of 110° C. and a weight of 5 kg.

TABLE-US-00004 TABLE 4 Composition of a conventional thermally expandable composition. C-R1 Ingredients P1 [wt.-%] 31 P2 [wt.-%] 18 AP [wt.-%] 14 Tackifier [wt.-%] 6 Acrylate [wt.-%] 0.5 Dispersion aid [wt.-%] 6 Stabilizer [wt.-%] 0.5 Filler [wt.-%] 10 ZnO [wt.-%] 4 ACDA [wt.-%] 8 PE [wt.-%] 2 TOTAL 100.0 Properties MFI [g/10 min] 25

[0163] For producing the non-inventive thermally expandable reference composition C-R1, the following procedure was followed:

[0164] In a first step, polymer P1 and polymer P2, the adhesion promoter, and the dispersion aid were mixed and melted at 95° C. with a mixing rate of 50 rpm (rounds per minute) during 10 min (minutes). After this, half of the activator amount was added during 1 min and mixing was continued during 4 min at 50 rpm. Mixing was continued at 20 rpm during 5 min until the mixture cooled down to 95° C.

[0165] After this, the azodicarbonamide, acrylate, and the second half of the activator amount were added during 1 min, followed by mixing at 50 rpm for 1 min. Finally the peroxide and all the rest were added during 1 min and mixing was continued for 2 min at 50 rpm.

[0166] The mixtures were molded with a temperature of 90° C. and a pressure of 60 bar during 15 s (seconds) into test shapes with a dimension of 25×25×3 mm (millimeters). These test shapes were cooled down to room temperature (23° C.) and used for the subsequently described expansion test experiments.

1.4 Thermally Expandable Compositions Based on Master-Batches

[0167] An inventive thermally expandable composition C-1 was produced by mixing 50 wt.-% of master-batch E1 and 50 wt.-% of thermally expandable reference composition C-R1 and extruding the mixture at a temperature of 100° C. Thereby, the blowing agent (ACDA, cf. table 1) of the thermally expandable composition C-R1 is introduced to composition C-1 as a component of reference composition C-R1.

[0168] For reasons of comparison, a thermally expandable reference composition C-R2 was produced by mixing 50 wt.-% of master-batch R3 (not according to the invention) and 50 wt.-% of thermally expandable reference composition C-R1 and extruding the mixture at a temperature of 100° C.

[0169] The mixtures were molded with a temperature of 90° C. and a pressure of 60 bar during 15 s (seconds) into test shapes with a dimension of 25×25×3 mm (millimeters). These test shapes were cooled down to room temperature (23° C.) and used for the subsequently described expansion test experiments.

2. Testing of Compositions

2.1 Volume Expansion and Stability Under Humid Conditions

[0170] For the volume expansion tests, the samples of thermally expandable compositions were baked during 30 min in an oven at a temperature of 205° C.

[0171] Expansions were quantified for each sample by measuring the density before and after expansion. The densities were determined according to DIN EN ISO 1183:2019 using the water immersion method (Archimedes principle) in deionized water and a precision balance to measure the mass.

[0172] In a first set of experiments, the initial volume expansions of the samples were measured directly after production. The magnitude of initial expansion before water treatment (in % based on the original volume prior to expansion) are shown in Table 5.

[0173] In a second set of experiments, the samples of the thermally expandable compositions were stored immersed in water at room temperature and tested daily for volume expansion. As long as the volume expansion exceeded the target range>1,500%, the samples were considered stable. In table 5, the time periods during which the samples remain stable are given.

TABLE-US-00005 TABLE 5 Volume expansion and stability under wet conditions of selected samples of thermally expandable compositions. Composition Expansion Stability C-R1 2′200% 5 days C-R2  .sup. 650% — C-1 1′950% >3 weeks.sup.# .sup.#After 3 weeks, the volume expansion still was 1′700%. No measurements have been taken afterwards.

[0174] As evident from table 5, similar to the conventional thermally expandable composition C-R1, the inventive thermally expandable composition C-1 shows an expansion well above the target range of >1,500%. However, the expansion of reference composition C-R2, which was produced with the non-inventive master-batch R3 having an MFI above the claimed range (>8 g/10 min), clearly is below the target range.

[0175] Further tests with thermally expandable composition which were based on master-batches having an MFI<0.1 g/10 min (not shown) could not be expanded to more than 650%, probably due to a too high degree of cross-linking.

[0176] With regard to stability, it is evident, that the inventive thermally expandable composition C-1 has a much better resistance to humidity or water, respectively, when compared with the conventional composition C-R1.

2.2 Rheological Properties

[0177] In order to determine rheological properties, the storage modulus (G′) and the loss modulus (G″) of selected samples have been determined with an ARES rotational rheometer (TA Instruments, New Castle, USA) 14 days after production.

[0178] FIG. 1 shows the storage modulus (G′) and the loss modulus (G″) of the sample made from the conventional composition C-R1 as a function of temperature whereas FIG. 2 show the storage modulus (G′) and the loss modulus (G″) of the sample made from the inventive thermally expandable composition C-1.

[0179] Interestingly, with increasing temperature, the sample based on the inventive composition C-1 (FIG. 2) becomes softer but it does not melt (no crossing of G′ and G″). In contrast, at temperatures of about 95° C., the reference sample based on the conventional composition C-R1 (FIG. 1) starts melting (crossing of the curves if G′ and G″). Thus, with regard to sagging during curing, the sample based on the inventive composition C-1 is clearly beneficial.

2.3 Adhesion Tests

[0180] Adhesion properties of selected samples were analyzed on metal as well as on nylon panels with a single lap shear test.

Metal Panels

[0181] Metal panels measuring 4″×6″ from cold rolled steel (CRS) and hot dipped galvanized (HDG) metal were cut on a metal cutter in an oven room. Half of the total metal panels were oiled using 60 μL of oil (Errocote® 61-MAL-HCl-1) for each metal panel and allowed to dwell for one hour before wiping off the excess. These panels were then used to make oiled sandwich panels.

[0182] Samples of C-R1 or C-1, respectively, were cut into 1″×3″×2.5 mm strips and placed on the metal panels.

[0183] In order to produce the sandwich structures, a spacer (length of the spacer: 10 mm; height if the spacer: 5 mm) was placed at both ends of the sample bearing panel, then another panel was placed on top of the spacers. These panels were held together with binder clips and then placed in an oven for 30 minutes at 190° C. Once baking was finished, the panels were removed and allowed to cool for one day at room temperature before evaluation.

[0184] Evaluating the sandwiched panels was effected be simply pulling the metal panels of a sandwich structure in opposite directions.

[0185] Both, sandwich panels containing the expanded C-R1 based sample material as well as the expanded C-1 based sample materials (with and without oil) adhered well. Failure exhibited was cohesive failure.

Nylon Panels

[0186] Panels of nylon (3 types: (i) normal nylon, (ii) nylon containing 35% glass fibers and (iii) nylon containing 15% carbon fibers) were cut into 4″×6″ panels and then aged for either (a) 1 week at a temperature of 50° C. at a humidity of 95% or (b) for 1 week at a temperature of 40° C. at a standard humidity. A further set of panels was also produced whereby water was sprayed directly onto the nylon panels for 30 seconds in a swirling pattern at the center of the panel.

[0187] Once aged or pre-treated with water, respectively, sample material based on C-R1 or C-1, respectively, was applied onto the nylon panels. Subsequently, the panels were placed in electric oven for 30 minutes at 190° C. Afterwards panels were cooled down to room temperature before evaluating the adhesion properties

[0188] Both, panels containing the expanded C-R1 based sample material as well as the expanded C-1 based sample materials adhered well on all types of nylon panels and independently of the ageing or the pre-treatment. Failure exhibited was cohesive failure.

2.4 Buckling Test

[0189] Additionally, buckling properties of selected samples were evaluated. Thereby, samples based on C-R1 or C-1, respectively, were produced with a thickness of 2.5 mm. Once affixed in the buckling tester, the samples were baked for 20 minutes at a temperature of 170° C.

[0190] Both, expanded C-R1 based sample materials as well as expanded C-1 based sample materials, adhered passed the buckling test (no deep buckling observed by visual inspection).

2.5 Emission Tests

[0191] Emission tests for acetaldehyde and formaldehyde with samples made from C-R1 based materials as well as C-1 based materials were performed according to standard VDA 276 “Determination of organic emissions from components for vehicle interiors with a 1 m.sup.3 test chamber” (VDA—Verband Deutscher Automobilindustrie, December 2005). Results are given in table 6.

TABLE-US-00006 TABLE 6 Emission of acetaldehyde and formaldehyde. Composition Formaldehyde [μg/m.sup.3] Acetaldehyde [μg/m.sup.3] C-R1 7.8 87.1 C-1 0.2 30.1

[0192] Thus, with C-1 based materials (according to the invention), both the emission of acetaldehyde and formaldehyde is significantly lower when compared to conventional C-R1 based materials.