Polyamide Hot Melt Coating

Abstract

The present invention relates to a thermoplastic coating composition comprising at least one polyamide and at least one surface modifying agent, wherein the polyamide comprises a reaction product of: a) at least one dimerized fatty acid; b) at least one mono carboxylic acid; c) at least one linear dicarboxylic acid; and d) at least one linear diamine;
wherein the surface modifying agent is selected from slip agents, anti-blocking agents or combinations thereof; wherein the surface modifying agent is contained in 0.1 to 10 wt-%, based on the total weight of the thermoplastic coating composition; and wherein the composition preferably has a coefficient of friction (COF) of 0.2 to 1.1 which is measured according to ASTM D 1894.

Claims

1. A thermoplastic coating composition comprising: at least one polyamide, wherein the polyamide comprises a reaction product of: a) at least one dimerized fatty acid; b) at least one mono carboxylic acid; c) at least one linear dicarboxylic acid; and d) at least one linear diamine; and 0.1 to 10 wt-%, based on the total weight of the thermoplastic coating composition of at least one surface modifying agent selected from slip agents, anti-blocking agents or combinations thereof.

2. The thermoplastic coating composition according to claim 1, wherein the composition preferably has a coefficient of friction (COF) of 0.2 to 1.1 measured according to ASTM D 1894.

3. The thermoplastic coating composition according to claim 1, wherein the at least one mono carboxylic acid b) is selected from the group consisting of linear C3 to C24 mono carboxylic acids, branched C3 to C24 mono carboxylic acids or combinations thereof.

4. The thermoplastic coating composition according to claim 1, wherein the at least one mono carboxylic acid b) is selected from the group consisting of linear C12 to C18 mono carboxylic acids, branched C12 to C18 mono carboxylic acids or combinations thereof.

5. The thermoplastic coating composition according to claim 1, wherein the at least one linear dicarboxylic acid c) is at least one linear C6 to C18 dicarboxylic acid.

6. The thermoplastic coating composition according to claim 1, wherein the at least one linear dicarboxylic acid c) is at least one linear C10 to C14 dicarboxylic acid.

7. The thermoplastic coating composition according to claim 1, wherein the at least one linear diamine d) is at least one linear aliphatic diamine having C1 to C10 carbon atoms.

8. The thermoplastic coating composition according to claim 1, wherein the at least one linear diamine d) is at least one linear aliphatic diamine having C2 to C6 carbon atoms.

9. The thermoplastic coating composition according to claim 1, wherein the at least one linear diamine d) is 1,2-ethylene diamine.

10. The thermoplastic coating composition according to claim 1, wherein the equivalent ratio of NH.sub.2 groups of d) to the sum of the COOH groups of a) to c) is from 1.2:1 to 1:1.2.

11. The thermoplastic coating composition according to claim 1, wherein the surface modifying agent is selected from alumina, silica, glass microspheres, wax, a perfluoro compound, a poly(meth)acrylate, a fatty acid amide, a polysiloxane and combinations thereof.

12. The thermoplastic coating composition according to claim 1, comprising 0.1 wt.-% to 3 wt.-% surface modifying agent based on the total weight of the thermoplastic coating composition.

13. The thermoplastic coating composition according to claim 1, further comprising 0.1 to 20 wt.-%, based on the total weight of the thermoplastic coating composition, of at least one additive different from the surface modifying agent and selected from antioxidants, fillers, pigments, plasticizers, polymers different from the polyamide, tackifiers, and combinations thereof.

14. The thermoplastic coating composition according to claim 1, further comprising 0.1 to 10 wt.-%, based on the total weight of the thermoplastic coating composition, of pigments.

15. The thermoplastic coating composition according to claim 1, having a ring and ball softening point of 90 to 220 C. or of 110 to 190 C. or of 140 to 170 C.

16. An article having an exterior surface and comprising on at least a portion of the surface a coating of the thermoplastic coating composition according to claim 1.

17. The article of claim 16 being a writing utensil, a wooden pencil, a packaging material, a toy, furniture, a decorative plate, or a houseware.

18. An article having an exterior surface selected from a wooden surface, a plastic surface or a wood-plastic-composite surface and comprising on at least a portion of the surface a coating of the thermoplastic coating composition according to claim 1.

19. A method of coating a surface comprising the steps of: providing an article having an external surface; providing the thermoplastic coating composition according to claim 1; melting the thermoplastic coating composition; applying the melted thermoplastic coating composition through an extruder at least a portion of the external surface of the article to form a finished coating; and cooling the coating to a solid state.

20. The method of claim 19 wherein the article is a writing utensil, a wooden pencil, a packaging material, a toy, furniture, a decorative plate, or a houseware and the finished coating is provided by a single application of the melted thermoplastic coating composition to the portion of the external surface of the article.

Description

EXAMPLES

[0066] The thermoplastic coating composition according to the present invention can be prepared as follows. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

General Preparation Method

[0067] In a 5-neck round bottom flask with mechanical stirrer and under inert atmosphere (nitrogen gas) all acid components (components a) to c)), an optional acid catalyst and antioxidants were added at room temperature (about 25 C.) and heated to 120 C. Then the linear diamine (compound d)) was drop wise added. The system was heated to 220 C. for about 1 hour and the water was distilled off under vacuum (30 mbar). Subsequently, nitrogen gas was supplied into the flask to restore atmospheric pressure and the temperature was cooled to 200 C. Then the modifying agent was added to the mixture. After 30 minutes under stirring the final molten mixture was carefully poured out of the flask into a wide non-sticky tray and allowed to cool to room temperature in order to obtain the final coating composition.

Polyamide 1 (P1)

[0068] For polyamide 1, 85.2 wt.-% dimer fatty acid (36 carbon atoms), 1 wt.-% stearic acid (18 carbon atoms) and 3.2 wt.-% sebacic acid (10 carbon atoms) were reacted according to the above mentioned procedure with 10 wt.-% of 1,2-ethylene diamine.

Polyamide 2 (P2)

[0069] For polyamide 2, 80.5% wt.-% dimer fatty acid (36 carbon atoms), 1% wt.-% stearic acid (18 carbon atoms, linear mono carboxylic acid) and 7 wt.-% tetradecandioic acid (14 carbon atoms, dicarboxylic acid) were reacted according to the above mentioned procedure with 10 wt.-% of 1,2-ethylene diamine.

TABLE-US-00001 TABLE 1 (examples and comparative example) Ring & ball Viscosity at Ex. Polyamide Surface modifying agent COF softening point 210 C. 1 P1 (99.3 wt.-%) microcrystalline paraffin 0.34 (3 days) 156.2 C. 7600 mPas wax (0.2 wt.-%) 2 P1 (98.4 wt.-%) high surface area fumed 0.34 (3 days) 155.3 C. 7975 mPas alumina (1.0 wt.-%); microcrystalline paraffin wax (0.1 wt.-%) 3 P1 (99.0 wt.-%) stearyl erucamide 1.01(immediate) Not Not (0.5 wt.-%) 0.21 (3 days) measured measured C4 P2 (99.5 wt.-%) none 1.15(immediate) 163.5 C. 7900 mPas 0.87 (3 days) 5 P2 (99.2 wt.-%) microcrystalline paraffin 0.76(immediate) 163.7 C. 8850 mPas wax (0.3 wt.-%) 0.36 (3 days) 6 P2 (98.7 wt.-%) microcrystalline paraffin 0.51 (immediate) 163.8 C. 7875 mPas wax (0.3 wt.-%); 0.39 (3 days) behenamide (0.5 wt.-%)
Example C4 is a comparative example. All examples additionally contained 0.1 wt.-% Irganox 1010 (BASF AG, Ludwigshafen, Germany) and 0.4 wt.-% Ralox 46 (Raschig GmbH, Ludwigshafen, Germany), both are antioxidants. COF and ring & ball softening point were measured as defined above.

[0070] From the experiments, it can be seen that a desired coating, having a low coefficient of friction, is only obtained by employing specific polyamides of the present invention in combination with at least one surface modifying agent.