Liquid modifier as carrier system for CFAs in foamed polystyrenes

Abstract

The invention relates to a liquid formulation for foaming a thermoplastic polystyrene, said formulation comprising a) a liquid carrier; and b) at least one endothermic chemical blowing agent selected from the group consisting of dicarboxylic acids, tricarboxylic acids, salts of dicarboxylic acids, salts of tricarboxylic acids, esters of dicarboxylic acids and esters of tricarboxylic acids.

Claims

1. A liquid formulation for foaming a thermoplastic polystyrene, said formulation comprising a) 25-90 wt. %, based on the total weight of the liquid formulation, of a liquid carrier; and b) 10 to 75 wt.-%, based on the total weight of the liquid formulation, of at least one endothermic chemical blowing agent selected from the group consisting of tricarboxylic acids, salts of tricarboxylic acids, oxalic acid, oxalic acid salts, succinic acid, succinic acid salts, adipic acid, adipic acid salts, phthalic acid, and phthalic acid salts; wherein the liquid formulation does not include a (bi)carbonate foaming agent, and wherein the liquid carrier is selected from paraffinum liquidum, acetylated monoglyceride, or a mixture thereof.

2. The formulation as claimed in claim 1, wherein the formulation is a dispersion and wherein the endothermic chemical blowing agent is dispersed in the liquid carrier.

3. The formulation as claimed in claim 1, wherein the endothermic chemical blowing agent is selected from the group consisting of succinic acid, succinic acid salts, adipic acid, adipic acid salts, phthalic acid, phthalic acid salts, citric acid, and citric acid salts.

4. The formulation as claimed in claim 1, wherein the endothermic chemical blowing agent is selected from the group consisting of citric acid, and citric acid salts.

5. The formulation as claimed in claim 1, wherein the liquid carrier comprises an aqueous medium, an organic solvent-based medium, an oil-based medium or a combination thereof.

6. The formulation as claimed in claim 1, wherein the liquid carrier comprises a vegetable oil, a mineral oil, an acetylated monoglyceride, a sorbitan oleate, an ethoxylated sorbitan oleate or a mixture thereof.

7. The formulation as claimed in claim 1, further comprising customary additives selected from the group consisting of colorants, stabilizers, antioxidants, antibacterial agents, neutralizers, antistatic agents, antiblocking agents, optical brighteners, heavy metal inactivation agents, hydrophobic agents, peroxides, water scavengers, acid scavengers, hydrotalcites, elastomers, impact modifiers, laser marking additives, processing aids and mixtures thereof.

8. The formulation as claimed in claim 1, further comprising c) 0.0001 to 15 wt.-% of customary additives, based on the total weight (100%) of the liquid formulation.

9. The formulation as claimed in claim 1, comprising a) 30 to 60 wt.-% of a liquid carrier, b) 70 to 40 wt.-%, of the at least one endothermic chemical blowing agent, and optionally c) 0.1 to 7.5 wt.-% of customary additives, based on the total weight (100%) of the liquid formulation.

10. A foamed thermoplastic polystyrene material foamed by a liquid formulation as claimed in claim 1.

11. A method of making a polystyrene foam material comprising the step of contacting a thermoplastic polystyrene and a liquid formulation according to claim 1 during melt processing under such conditions that the liquid formulation produces gas which foams the polystyrene.

12. The method as claimed in claim 11, wherein the thermoplastic polystyrene is a styrene homopolymer, an alkylstyrene homopolymer, a high-impact polystyrene or a mixture thereof.

13. A liquid formulation for foaming a thermoplastic polystyrene, said formulation comprising: a) 25-90 wt. %, based on total weight of the liquid formulation, of a liquid carrier selected from paraffinum liquidum, acetylated monoglyceride, or a mixture thereof; and b) 10-75 wt. %, based on total weight of the liquid formulation, of at least one endothermic chemical blowing agent selected from succinic acid, succinic acid salts, succinic acid esters, adipic acid, adipic acid salts, adipic acid esters, phthalic acid, phthalic acid salts, phthalic acid esters, citric acid, citric acid salts, or citric acid esters; wherein the liquid formulation is a dispersion and wherein the endothermic chemical blowing agent is dispersed in the liquid carrier.

14. The formulation as claimed in claim 13, wherein the endothermic chemical blowing agent is selected from the group consisting of succinic acid, succinic acid salts, adipic acid, adipic acid salts, phthalic acid, phthalic acid salts, citric acid, and citric acid salts.

15. The formulation as claimed in claim 13, wherein the endothermic chemical blowing agent is selected from the group consisting of citric acid, and citric acid salts.

16. A foamed thermoplastic polystyrene material foamed by a liquid formulation as claimed in claim 13.

Description

EXAMPLES

(1) The following materials are used:

(2) CFA 1a: monosodium citrate

(3) CFA 2b: sodium bicarbonate (comparison)

(4) PS: 158 N Styrolution:Styrolution PS 486N HIPS=1:1

(5) PE: LDPE Sabic 1965N0 (comparison)

(6) Liquid Media:

(7) 4B: paraffinum liquidum (density 0.85 g/ml at 20° C.)

(8) 6B acetylated monoglyceride:

(9) Preparation of Liquid Dispersions:

Example 1

(10) 500 g of dispersion were prepared by initially mixing liquid medium 4B (400 g) and 100 g of CFA 1a. Mixing was initially undertaken manually to start incorporating the solid materials in the liquid. Subsequently, mixing was continued in a high speed mixer with cowls disc with 3000 rounds per minute for 15 to 30 minutes, while increasing the temperature to 40 to 50° C.

(11) Thus, a dispersion was prepared comprising

(12) Liquid medium 4B: 80 wt.-%

(13) Monosodium citrate: 20 wt.-%

Example 2

(14) 500 g of dispersion were prepared by initially mixing liquid medium 4B (300 g) and 200 g of CFA 1a. Mixing was initially undertaken manually to start incorporating the solid materials in the liquid. Subsequently, mixing was continued in a high speed mixer with cowls disc with 3000 rounds per minute for 15 to 30 minutes, while increasing the temperature to 40 to 50° C.

(15) Thus, a dispersion was prepared comprising

(16) Liquid medium 4B: 60 wt.-%

(17) Monosodium citrate: 40 wt.-%

Example 3

(18) 500 g of dispersion were prepared by initially mixing liquid medium 6B (400 g) and 100 g of CFA 1a. Mixing was initially undertaken manually to start incorporating the solid materials in the liquid. Subsequently, mixing was continued in a high speed mixer with cowls disc with 3000 rounds per minute for 15 to 30 minutes, while increasing the temperature to 40 to 50° C.

(19) Thus, a dispersion was prepared comprising

(20) Liquid medium 6B: 80 wt.-%

(21) Monosodium citrate: 20 wt.-%

Example 4

(22) 500 g of dispersion were prepared by initially mixing liquid medium 6B (300 g) and 200 g of CFA 1a. Mixing was initially undertaken manually to start incorporating the solid materials in the liquid. Subsequently, mixing was continued in a high speed mixer with cowls disc with 3000 rounds per minute for 15 to 30 minutes, while increasing the temperature to 40 to 50° C.

(23) Thus, a dispersion was prepared comprising

(24) Liquid medium 6B: 60 wt.-%

(25) Monosodium citrate: 40 wt.-%

Example 5 (Comparative)

Solid Formulation

(26) 500 g of a solid formulation were prepared by initially mixing 400 g of polyethylene pellets (LDPE, SABIC 1965N0) and 100 g of CFA 1a. Subsequently, the physical mixing was accomplished by melting the mixture in an extruder at a temperature of ° C. and forming pellets thereof.

(27) Thus, a solid formulation was prepared comprising

(28) PE: 80 wt.-%

(29) Monosodium citrate: 20 wt.-%.

Example 6 (Comparative)

Liquid Formulation, Bicarbonate as CFA 2b

(30) 500 g of dispersion were prepared by initially mixing liquid medium 4B (400 g) and 100 g of CFA 2b. Mixing was initially undertaken manually to start incorporating the solid materials in the liquid. Subsequently, mixing was continued in a high speed mixer with cowls disc with 3000 rounds per minute for 15 to 30 minutes, while increasing the temperature to 40 to 50° C.

(31) Thus, a dispersion was prepared comprising

(32) Liquid medium 4B: 80 wt.-%

(33) Sodium bicarbonate: 20 wt.-%

Example 7 (Comparative)

Liquid Formulation, Bicarbonate as CFA 2b

(34) 500 g of dispersion were prepared by initially mixing liquid medium 6B (400 g) and 100 g of CFA 2b. Mixing was initially undertaken manually to start incorporating the solid materials in the liquid. Subsequently, mixing was continued in a high speed mixer with cowls disc with 3000 rounds per minute for 15 to 30 minutes, while increasing the temperature to 40 to 50° C.

(35) Thus, a dispersion was prepared comprising

(36) Liquid medium 6B: 80 wt.-%

(37) Sodium bicarbonate: 20 wt.-%

(38) Manufacture of the Films:

(39) Different parts of the liquid (or solid) formulations (ref. on Table 1) of Examples 1 to 7 were mixed with different parts of PS (158 N Styrolution:Styrolution PS 486N HIPS=1:1) on a coex-film line at a temperature of 180-220° C. ° C. The film structure was a three-layer film ABA (25%/50%/25%) where the middle layer was equipped with the CFA formulation. The results are shown in Table 2

(40) TABLE-US-00001 TABLE 1 CFA CFA Part of carrier content content (liquid or solid) Type of Carrier in batch in film in film Example CFA system [%] [%] [%] 1 1a 4B 20 0.35 1.75 2 1a 4B 40 0.5 1.25 3 1a 6B 20 0.35 1.75 4 1a 6B 40 0.5 1.25 5 (comp.) 1a PE 20 0.35 1.75 6 (comp.) 2b 4B 20 0.35 1.75 7 (comp.) 2b 6B 20 0.35 1.75

(41) TABLE-US-00002 TABLE 2 Test results Cell size in Cell size in machine transverse direction direction Strain horizontal/ horizontal/ Cell Young's at vertical vertical Density volume modulus break Example [μm] [μm] [g/ml] [μm.sup.3] [MPa] [%] 1 42/114 37/60 0.848 153 1700 11 2 47/106 35/65 0.835 167 1700 11 3 34/140 35/70 0.858 167 1850 11 4 36/110 38/62 0.828 129 1700 11 5 (comp) 65/117 55/98 0.815 388 1700 7 6 (comp) 63/155 50/89 0.838 454 1700 9 7 (comp) 50/178 52/94 0.836 438 1750 10

(42) Investigations on mechanical properties were performed using a stress-strain machine (Zwick/Roell Frank8103Mops-F, Ulm, Germany) compliant with ISO 527-1/2 to obtain the Young's Modulus and strain at break. The results are the averaged values of five measurements.

(43) As it is shown in table 2 the liquid carrier system effects a cell size reduction of about 60%. The carrier system (liquid or solid carrier) also influences the mechanical properties of the foamed part. While the stiffness, expressed by Young's Modulus, remains constant mainly independent of the carrier system, the flexibility of the foamed material, expressed by strain at break, is significantly influenced by the carrier system. The strain at break of liquid carrier systems increases up to 57% compared to the solid carrier system. Therefore, it is proven that liquid carrier systems cause a modifying effect to improve the mechanical properties.

(44) It is further shown in Table 2 that the type of CFA influences the foam structure and the strain at break. Both are disadvantageously influenced when replacing the CFA according to the invention by a bicarbonate of the art.