COMPRESSION LIMITER

Abstract

The present invention relates to a compression limiter made of a first thermoplastic composition comprising a semi-crystalline semi-aromatic polyamide. The invention further relates to a process for producing the compression limiter, and to an assembly comprising the compression limiter and a thermoplastic body made of a second thermoplastic polyamide composition. According to the invention, the compression limiter is made of a thermoplastic composition.

Claims

1. Compression limiter made of a thermoplastic material, wherein the thermoplastic material comprises (A) 35-65 wt. % of a polyamide component (A), wherein at least 90 wt. % of the polyamide component (A) consists of a semi-crystalline semi-aromatic polyamide (A-1), consisting of repeat units derived from 45-50 mole % of a diamine, 40-50 mole % of an aromatic dicarboxylic acid; and 0-10 mole % of one or more other monomers, wherein the mole % is relative to the total molar amount of diamine, aromatic dicarboxylic acid and one or more other monomers, and wherein (A-1) has a glass transition temperature (Tg) of at least 110° C. and a melting temperature of at least 280° C.; and (B) 35-65 wt. % of a fibrous reinforcing agent, wherein the weight percentages of (A) and (B) are relative to the total weight of the composition.

2. Compression limiter according to claim 1, wherein the semi-crystalline semi-aromatic polyamide (A-1) has a glass transition temperature (Tg) in the range of 120-170° C. and a melting temperature in the range of 290-340° C.

3. Compression limiter according to claim 1, wherein at least 70 mole % of the diamine is a linear or branched aliphatic C4-C10 diamine, or a cycloaliphatic diamine, or a combination thereof at least 70 mole % of the aromatic dicarboxylic acid is terephthalic acid, naphthalene dicarboxylic acid or biphenyl dicarboxylic acid, or a combination thereof the amount of repeat units derived one or more other monomers is 0-5 mole %, wherein the mole % is relative to the total molar amount of diamine, aromatic dicarboxylic acid and one or more other monomers.

4. Compression limiter according to claim 1, wherein polyamide component (A) is present in an amount of 40-60 wt. % the fibrous reinforcing agent (B) is present in an amount of 40-60 wt. %; 0-10 wt. % of inorganic filler; 0-5 wt. % of another polymer; and 0-5 wt. % of at least one additive; wherein the weight percentages of (A) to (E) are relative to the total weight of the composition and the combined amount of (A)-(E) is 100 wt. %.

5. Compression limiter according to claim 1, wherein the reinforcing agent comprises glass fibers or carbon fibers, or a combination thereof.

6. Compression limiter according to claim 1, wherein the thermoplastic material has an elastic modulus at 23° C. of at least 10,000 MPa, preferably at least 12,500 MPa, and more preferably at least 15,000 MPa, and an elastic modulus at 200° C. of at least 4,000 MPa, preferably at least 5,000 MPa, and more preferably at least 6,000 MPa.

7. Compression limiter according to claim 1, wherein the compression limiter comprising a main body having a cylindrical shape, optionally a tapered cylindrical shape, or an outer surface comprising recessions or protrusions, or a flanged end, or any combination thereof.

8. Assembly comprising a thermoplastic body and at least one compression limiter, wherein the compression limiter is made of a first thermoplastic polyamide polymer composition and the thermoplastic body is made of a second polyamide polymer composition and wherein the first polyamide polymer composition has a composition as defined in claim 1.

9. Assembly according to claim 8, wherein the first thermoplastic material has an elastic modulus at 23° C. at least fifty percent (50%) greater than the elastic modulus at 23° C. of the second polymer composition.

10. Assembly according to claim 8, wherein the second thermoplastic material comprises a polymer component at least 50 wt. % thereof consisting of a thermoplastic aliphatic polyamide, preferably chosen from PA-6, PA-66, PA46 and PA-410, and any copolyamide thereof.

11. Assembly according to claim 8, wherein the assembly is an engine front cover, an intake manifold, an actuator housing or a part of a charging connector or a high voltage switch assembly.

12. Process for producing an assembly according to claim 8, comprising steps of providing a mold with a cavity; providing at least one compression limiter in the cavity, injection molding of a second thermoplastic polyamide composition into the cavity, thereby overmolding the compression limiter with the second thermoplastic polyamide composition and producing an injection molded thermoplastic body, and removing the injection molded thermoplastic body with the overmolding the compression limiter integrated therein from the cavity wherein the at least one compression limiter is made of first polyamide polymer composition.

13. Use of an assembly according to claim 8 in engines, automotive power train systems, industrial machinery or electronic products.

14. Construction comprising an assembly according to claim 8 mounted on a carrier, preferably mounted with at least one bold having a flange passing through a compressing limiter in the assembly or with a bold passing through a washer and the compressing limiter, the compressing limiter having an end section, wherein the surface of the washer or bold flange at least overlaps with and preferably extends beyond the surface of the end section of the compression limiter.

Description

EXAMPLE 1

[0096] A mold was provided with a cylindrical cavity, outer diameter 14.4 mm, inner diameter 7.2 mm, and a length of approximately 28 mm. The PPA-1 was melt extruded and injected into the mold cavity using a standard extruder (single screw extruder) and injection molding machine. The setting temperature of the T-melt in the injection molding machine was about 350° C.; the temperature of the mold was about 140° C. The molded part was removed from the mold, thereby obtaining the injection molded compression limiter. Three specimens of the injection molded compression limiter of Example 1 were further tested as described herein above in Methods of testing.

COMPARATIVE EXPERIMENT A

[0097] Example 1 was repeated except that APA 1 was used instead of PPA-1. The setting temperature of the T-melt in the injection molding machine was about 295° C.; the temperature of the mold was about 70° C.

EXAMPLE 2

[0098] A mold was provided with a cavity having a three dimensional shape. The injection molded compression limiter of Example 1 was placed in the mold. The polymer composition APA-1 was melt extruded and injected into the mold cavity thereby overmolding the compression limiter. The molded part was removed from the mold, thereby obtaining the injection molded assembly of Example 2. Example 2 was repeated twice. Two specimens of the assembly of Example 2 were further tested.

COMPARATIVE EXPERIMENT B

[0099] The production of the assembly of Example 2 was repeated except that instead of the injection molded compression limiter of Example 1, a metallic compression limiter was placed into the mold, and the metallic compression limiter was overmolded with APA-1.

COMPARATIVE EXPERIMENT C

[0100] The production of the assembly of example 2 was modified such that instead of the injection molded compression limiter of Example 1, the compression limiter of Comparative A was placed into the mold, and overmolded with APA-1.

Testing of the Compression Limiters

[0101] One specimen of each of the compression limiters were subjected to a compression test in a mechanical test apparatus as described herein above. The compression limiter of Example 1 withstood a much larger static compression failure force than the compression limiter of Comparative A (results obtained in Table 1).

[0102] Another specimen of each of the assemblies was subjected to a compression test wherein the retention of the compression force was tested. With the assembly of Comparative C the retention of the compression force was much worse compared to that of Example 1.

[0103] The results presented in Tables 1 and 2 demonstrate that the compression limiter according to the present invention showed high load-bearing properties over a wide temperature range, i.e. high static compression failure force and retention of compression force at 23° C. and 120° C., this also indicating good sealing performance.

TABLE-US-00001 TABLE 1 Static compression Static compression failure force (kN) failure force (kN) Temperature Example 1 Comparative Example A  23° C. 27.5 21 120° C. 17 9.5

TABLE-US-00002 TABLE 2 After After After After Time 0 h 1 h 9 h 24 h Oven temperature 23° C. 23° C. 120° C. 23° C. Retention force (kN) 10 9.7 6.9 6.9 Example 1 Retention force (kN) 10 9.2 3.2 2.1 Comparative Experiment A