WO2014078125A1

WO2014078125A1 - Copolyamide compositions

Info

Publication number: WO2014078125A1
Application number: PCT/US2013/068446
Authority: WO
Inventors: Marvin M. Martens
Original assignee: E. I. Du Pont De Nemours And Company
Priority date: 2012-11-19
Filing date: 2013-11-05
Publication date: 2014-05-22

Abstract

Disclosed is a copolyamide including: a) 50 to 65 moi % of a first repeat unit of formula (I) and b) 35 to 50 mol % of a second repeat unit selected from the group consisting of formula (II), - C(O)(CH₂)_nC(O)NH(CH₂)₆NH- wherein n is an integer selected from 12, 14, and 16; the copolyamide having a melting point of at least 280 °C.

Description

Copolyamide Compositions

Field of Invention

The present invention relates to the field of semi-aromatic copolyamides derived, in part, from vegetable oils.

BACKGROUND OF INVENTION

The demand for renewable bio-based polymers having similar or better performance characteristics than petrochemical-based polymers, together with increasing fossil raw material prices, make it highly desirable to develop polyamides derived from renewable sources. Long chain dicarboxylic acids, derived from bio- based feedstocks are used in a variety of polymer products and other applications including poly(hexamethylene decanediamide (PA 610) and poly(hexamethylene dodecanediamide) (PA 612).

There is a need to replace PA 6T/66 (55/45), which has a melting point of 290 - 310 °C, with a copolyamide that is, at least in part, renewably sourced, and having a comparable high melt temperature. At the same time, improvement in water absorption and impact resistance is desired. Needed are copolyamides made from a renewable source, having a melt point of at least 280 °C, and having improved water resistance and better impact resistance than PA 6T/66 (55/45).

US patent application 2010/0233402 discloses a vehicular part comprising copolyamides comprising about 68 to about 82 molar percent of repeat units PA 610 or 612 and about 18 to about 32 molar percent of repeat units of PA 6T.

US patent application 2010/0028580 discloses poly(hexamethylene

tetradecanediamide/hexamethylene terephthalamide.

SUMMARY OF INVENTION

Disclosed is a copolyamide comprising:

a) 50 to 65 mol % of a first repeat unit of formula (I),

b) 35 to 50 mol % of a second repeat unit selected from the group consisting of formula (II) -C(O)(CH₂)nC(O)NH(CH₂)₆NH- (II); wherein n is an integer selected from 12, 14, and 16; said copolyamide has a melting point, as determined with differential scanning calorimetry (DSC) at a scan rate of 10 °C/min in the first heating scan, of at least 280 °C; and the mol % of repeat units are based on the total repeat units present in the copolyamide.

DETAILED DESCRIPTION

Herein melting points are as determined with differential scanning calorimetry (DSC) at a scan rate of 10 °C/min in the first heating scan, wherein the melting point is taken at the maximum of the endothermic peak, and the heat of fusion in

Joules/gram (J/g) is the area within the endothermic peak.

The Copolymers disclosed herein have two or more diamide molecular repeat units. The copolymers are identified by their respective repeat units. The following list exemplifies the abbreviations used to identify monomers and repeat units in the homopolymer and copolymer polyamides (PA) disclosed herein:

HMD 1 ,6-hexamethylene diamine (or 6 when used in combination with a diacid)

AA Adipic acid

T Terephthalic acid

14 Tetradecane dioic acid

16 Hexadecane dioic acid

18 Octadecanedioic acid

DDA Decanedioic acid

DDDA Dodecanedioic acid

66 polymer repeat unit formed from HMD and AA

610 polymer repeat unit formed from HMD and DDA

612 polymer repeat unit formed from HMD and DDDA

614 polymer repeat unit formed from HMD and tetradecane dioic acid

616 polymer repeat unit formed from HMD and hexadecane dioic acid

618 polymer repeat unit formed from HMD and octadecane dioic acid

6T polymer repeat unit formed from HMD and T. Note that in the art the term "6" when used alone designates a polymer repeat unit formed from€-caprolactam. Alternatively "6" when used in combination with a diacid such as adipic acid, for instance 66, the "6" refers to HMD. In repeat units comprising a diamine and diacid, the diamine is designated first. Furthermore, when "6" is used in combination with a diamine, for instance 66, the first "6" refers to the diamine HMD, and the second "6" refers to adipic acid. Likewise, repeat units derived from other amino acids or lactams are designated as single numbers designating the number of carbon atoms.

Copolymer repeat units are separated by a slash (that is, /). For instance poly(hexamethylene terephthamide/hexamethylene tetradecanediamide) is abbreviated PA614/6T (35/65), and the values in brackets are the mole % repeat unit of each repeat unit in the copolymer.

In one embodiment the copolyamide comprises:

b) 50 to 65 mol %, and preferably 50 to 60, and 52 to 58 mol % of a first

repeat unit of formula (I),

b) 35 to 50 mol %, and preferably 40 to 50, and 42 to 48 mol % of a second repeat unit selected from the group consisting of formula (II)

-C(O)(CH₂)nC(O)NH(CH₂)₆NH- (II); wherein and n is an integer selected from 12, 14, and 16; said copolyamide has a melting point, as determined with differential scanning calorimetry (DSC) at a scan rate of 10 °C/min in the first heating scan, of at least 280 °C; and the mol % of repeat units are based on the total repeat units present in the copolyamide. Preferably the copolyamide has a melting point between 280 °C and 320 °C and, more preferably, between 285 °C and 320 °C.

In one embodiment the copolyamide consists essentially of the ranges of repeat units, including the stated preferences, as disclosed above. The term "consist essentially of means the embodiment necessarily includes the listed repeat units and is open to unlisted repeat units that do not materially affect the basic and novel properties of the invention. Herein, for instance, the term as applied to the

copolyamide, means the copolyamide includes the repeat units of formula (I) and (II), and may include other repeat units in small amounts, so long as the additional repeat units do not materially affect the basic and novel properties of the invention. The basic properties of the copolyamides of this invention include a melting point of at least 280 °C; a moisture uptake of less than 2.0 weight percent when 4 mm test bars prepared from said copolyamide, and immersed in water at a test temperature of 23 °C for a test period of 100 days; and a % retention of tensile strength after the moisture uptake, as disclosed above, of at least 70 %, and preferably at least 80 %, as compared to a dry-as- molded control of identical composition.

In one embodiment the copolyamide consists essentially of 50 to 60 mol % of a first repeat unit of formula (I) and 40 to 50 mol % of a second repeat unit selected from the group consisting of formula (II). Another embodiment is a copolyamide, as disclosed above, wherein the first repeat unit of formula (I) is present at 52 to 58 mol % and the second repeat of formula (II) is present at 42 to 48 mol %.

Other embodiments are copolyamides comprising ranges of repeat units of formula (I) and (II), as disclosed above, wherein n = 12, 14 and 16, respectively. Other embodiments include copolyamides wherein 4 mm test bars prepared from said copolyamides, and immersed in water at a test temperature of 23 °C for a test period of 100 days, have a moisture uptake of less than 2.0 weight percent.

Other embodiments include copolyamides wherein 4 mm test bars prepared from said copolyamides have a % retention of tensile strength after the moisture uptake, as disclosed above, of at least 70 %, and preferably at least 80 %, as compared to a dry-as- molded control of identical composition.

The copolyamides of the invention are preferably prepared from aliphatic dioic acids and aliphatic diamines, at least one of which is bio-sourced or "renewable". By "bio-sourced" is meant that the primary feed-stock for preparing the dioic acid and/or diamine is a renewable biological source, for instance, vegetable matter including grains, vegetable oils, cellulose, lignin, fatty acids; and animal matter including fats, tallow, oils such as whale oil, fish oils, and the like. These bio-sources of dioic acids and aliphatic diamines have a unique characteristic in that they ail possess high levels of the carbon isotope ¹⁴C; as compared to fossil or petroleum sources of the dioic acids and aliphatic diamines. This unique isotope feature remains unaffected by non-nuclear, conventional chemical modifications. Thus the ¹⁴C isotope level in bio-sourced materials provides an unalterable feature that allows any downstream products, such as polyamides; or products comprising the polyamides, to be unambiguously identified as comprising a bio-sourced material. Furthermore, the analysis of ¹⁴C isotope level in dioic acids, diamines and downstream product is sufficiently accurate to verify the percentage of bio-sourced carbon in the

downstream product.

The copolyamides are prepared from aliphatic dioic acids and aliphatic diamines using conventional chemical methods as are well known in the art of polyamides. See, Kohan in "Nylon Plastics Handbook," Melvin I. Kohan, Ed., Hanser Publlishers (1995).

Preferred renewable copolyamides are wherein the repeat units (I) and (II) are prepared from C16 and C18 dioic acids derived from vegetable oils selected from the group consisting of soybean oil, palm oil, sunflower oil, olive oil, cotton seed oil, peanut oil and corn oil.

Materials

Tetradecanedioic acid having a melting point of 125 - 128 °C was obtained from Cathay Biotechechnology, Shanghai, China.

Hexadecanedioic acid refers to a material having a nominal melting point of 124 - 126 °C obtained from Cathay Biotechechnology, Shanghai, China.

Octadecanedioic acid refers to Emerox 118, having a melting point of 128- 130 °C, obtained from Emery Oleochemicals LLC, Ohio, US.

PA 6T/66 refers Zytel® HTN502HNC010copolyamide, made from terephthalic acid, adipic acid, and hexamethylenediamine; wherein the two acids are used in a 55:45 molar ratio; having a melting point of about 310 °C and an inherent viscosity (IV), according to ASTM D2857 method, typically about 1.07, available from E.I. DuPont de Nemours and Company, Wilmington, Delaware, USA.

Methods

Melting point Herein melting points were as determined with DSC at a scan rate of 10 °C/min in the first heating scan, wherein the melting point is taken at the maximum of the endothermic peak.

Inherent Viscosity

Inherent viscosity (IV) was measured on a 0.5% solution of copolyamide in tricresol at 25 °C.

Water absorption measurement:

The water absorption measurement was carried out by determining the increase in water uptake of injection molded bars upon immersion in water at 23 °C for 100 days. The test bars used were tensile bars with a thickness of 4 mm and a width of 10 mm. The bars were taken out from the vacuum sealed bags, weighed and immediately immersed in water bath maintained at 23 °C. The specimens were immersed in water for 100 days. After that, they were withdrawn, surface wiped and recorded the weights. The percentage increase in weight was calculated as per ASTM D570-98. All the test bars were tested immediately for physical properties. Physical properties measurement

ISO 527-1 A injection molded bars were molded with a mold temperature of 80 °C and melt temperature of 310 °C.

Tensile properties at 23 °C were measured as per ASTM D638 specification using an Instron tensile tester model 4469. Measurements were made on ISO 527- 1 A injection molded bars. The crosshead speed was 50 mm/min.

Flex strength was measured according to ISO 178 using 3-point bending. Measurements were made on ISO 527-1 A injection molded bars.

Notched izod was measured according to ISO 180 with ISO 527-1 A injection molded bars.

Examples 1 , 3 and 4

The ingredients listed in Table 1 were weighed into 14 inch long 1 inch diameter stainless steel tubes that were capped on one end. Four tubes were run at the same time for each Example. A pressure controller was connected to each tube. The four tubes were initially heated to 130 °C at atmospheric pressure with a sand bath to purge air from the tubes with steam. The pressure controllers were set for 320 psi and the tubes were heated to 280 °C in about 60 minutes. Steam began venting from the tubes during the heating to 280 °C. After reaching 280 °C, the pressure in each of the tubes was reduced from 320 psi to atmospheric over 45 minutes while increasing the temperature to 325 °C. The tubes were heated for an additional 30 minutes at atmospheric pressure and 325 °C before cooling. When the tubes were cool, they were opened and the polymer was removed as a solid plug.

Comparative Example C4

Comparative Example C4 was prepared in an identical manner to Example 1 described above except: after reaching 280 °C, the pressure in each of the tubes was reduced from 320 psi to atmospheric over 60 minutes while increasing the temperature to 330 °C. The tubes were heated for an additional 30 minutes at atmospheric pressure and 330 °C before cooling.

Example 2

Preparation of PA614/6T f 45/55)

Salt Preparation: A 10L autoclave was charged with tetradecanedioic acid

(1342 g), terephthalic acid (1055 g), an aqueous solution containing 76 weight % of hexamethylene diamine (HMD) (1774 g), an aqueous solution containing 28 weight percent acetic acid (30 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2330 g).

Polymerization process conditions: The autoclave agitator was set to 5 rpm and the contents were purged with nitrogen at 10 psi for 10 minutes. The agitator was then set to 50 rpm, the pressure control valve was set to 2.41 MPa (350 psi), and the autoclave was heated. The pressure was allowed to rise to 2.41 MPa at which point steam was vented to maintain the pressure at 2.41 Mpa. The

temperature of the contents was allowed to rise to 290 °C. The pressure was then reduced to 0 psig over about 45 minutes. During this time, the temperature of the contents rose to 315 °C. The autoclave pressure was reduced to 5 psia by applying vacuum and held there for approximately 20 minutes. The autoclave was then pressurized with 50 psi nitrogen and the molten polymer was extruded into strands, quenched with cold water and cut into pellets.

The polyamide obtained had an inherent viscosity (IV) of 1.09 dl/g. The polymer had a melting point of 288 °C.

Example 5

Preparation of PA616/6T (45/55)

A 10L autoclave was charged with hexadecanedioic acid (1432 g), terephthalic acid (1015 g), an aqueous solution containing 76 weight % of HMD (1708 g), an aqueous solution containing 28 weight percent acetic acid (30 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2330 g). Polymerization process conditions were the same as described earlier for Example 2. The polyamide obtained had an IV of 1.10 dl/g. The polymer had a melting point of 300 °C.

Example 6

Preparation of PA618/6T 45/55

A 10L autoclave was charged with octadecanedioic acid (1515 g), terephthalic acid (978 g), an aqueous solution containing 76 weight % of HMD (1646 g), an aqueous solution containing 28 weight percent acetic acid (30 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2360 g). Polymerization process conditions were the same as described earlier for Example 2 except that the finish temperature was 320 °C. The polyamide obtained had an IV of 0.98 dl/g. The polymer had a melting point of 301 °C.

Comparative Example C1

Preparation of PA614/6T 85/15

A 10L autoclave was charged with tetradecanedioic acid (2374 g), terephthalic acid (269 g), an aqueous solution containing 76 weight % of HMD (1667 g), an aqueous solution containing 28 weight percent acetic acid (21 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2190 g). Polymerization process conditions were the mostly the same as described earlier for Example 2 except that the reactor pressure was 1.72 MPa and the finish temperature was 260 °C. The polyamide obtained had an IV of 1.09 dl/g. The polymer had a melting point of 199 °C.

Comparative Example C2

Preparation of PA614/6T 75/25

A 10L autoclave was charged with tetradecanedioic acid (2150 g), terephthalic acid (461 g), an aqueous solution containing 76 weight % of HMD (1711 g), an aqueous solution containing 28 weight percent acetic acid (21 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2180 g). Polymerization process conditions were the mostly the same as described earlier for Example 2 except that the reactor pressure was 1.72 MPa and the finish temperature was 260 °C. The polyamide obtained had an IV of 1.13 dl/g. The polymer had a melting point of 192 °C.

Comparative Example C3

Preparation of PA614/6T 60/40

A 10L autoclave was charged with tetradecanedioic acid (1790 g), terephthalic acid (767 g), an aqueous solution containing 76 weight % of HMD (1728 g), an aqueous solution containing 28 weight percent acetic acid (21 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2230 g). Polymerization process conditions were the mostly the same as described earlier for Example 2 except that the reactor pressure was 2.07 MPa and the finish temperature was 285 °C. The polyamide obtained had an IV of 1.11 dl/g. The polymer had a melting point of 266 °C.

Comparative Example C5

Preparation of PA616/6T 85/15

A 10L autoclave was charged with hexadecanedioic acid (2263 g), terephthalic acid (232 g), an aqueous solution containing 76 weight % of HMD (1431 g), an aqueous solution containing 28 weight percent acetic acid (21 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2575 g). Polymerization process conditions were the mostly the same as described earlier for Example 2 except that the reactor pressure was 1.72 MPa and the finish temperature was 260 °C. The polyamide obtained had an IV of 1.14 dl/g. The polymer had a melting point of 187 °C.

Comparative Example C6

Preparation of PA616/6T 75/25

Salt Preparation and polymerization: A 10L autoclave was charged with hexadecanedioic acid (2061 g), terephthalic acid (399 g), an aqueous solution containing 76 weight % of HMD (1477 g), an aqueous solution containing 28 weight percent acetic acid (21 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2560 g). Polymerization process conditions were the mostly the same as described earlier for Example 2 except that the reactor pressure was 1.72 MPa and the finish temperature was 260 °C. The poiyamide obtained had an IV of 1.07 dl/g. The polymer had a melting point of 188 °C.

Comparative Example C7

Preparation of PA616/6T 70/30

A 10L autoclave was charged with hexadecanedioic acid (1955 g), terephthalic acid (486 g), an aqueous solution containing 76 weight % of HMD (1501 g), an aqueous solution containing 28 weight percent acetic acid (21 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2560 g). Polymerization process conditions were the mostly the same as described earlier for Example 2 except that the reactor pressure was 1.72 MPa and the finish temperature was 260 °C. The poiyamide obtained had an IV of 1.04 dl/g. The polymer had a melting point of 188 °C.

Comparative Example C8

Preparation of PA618/6T 85/15

A 10L autoclave was charged with octadecanedioic acid (2339 g), terephthalic acid (218 g), an aqueous solution containing 76 weight % of HMD (1338 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2610 g). Polymerization process conditions were the mostly the same as described earlier for Example 2 except that the reactor pressure was 1.72 MPa and the finish temperature was 260 °C. The poiyamide obtained had an IV of 1.04 dl/g. The polymer had a melting point of 185 °C.

Comparative Example C9

Preparation of PA618/6T 75/25

A 10L autoclave was charged with octadecanedioic acid (2142 g), terephthalic acid (377 g), an aqueous solution containing 76 weight % of HMD (1398 g), an aqueous solution containing 28 weight percent acetic acid (21 g), an aqueous solution containing 1 weight percent sodium hypophosphite (66 g), an aqueous solution containing 1 weight percent Carbowax 8000 (10 g), and water (2570 g). Polymerization process conditions were the mostly the same as described earlier for Example 2 except that the reactor pressure was 1.72 MPa and the finish temperature was 260 °C. The poiyamide obtained had an IV of 0.87 dl/g. The polymer had a melting point of 184 °C.

The data in Tables 2 and 3 indicate that within the range of 50 to 65 mol % 6T, the copolyamides have melting points between 280 °C and 320 °C which is desirable for molded articles having high melt temperatures.

Table 4 shows that Examples 2 and 5 have significantly lower moisture uptake than a conventional PA 6T/66 copolymer and have significantly improved % retention of tensile strength over the conventional PA 6T/66 copolymer.

Claims

CLAIMS We Claim:

1. A copolyamide comprising:

c) 50 to 65 mol % of a first repeat unit of formula (I),

b) 35 to 50 mol % of a second repeat unit selected from the group consisting of formula (II)

-C(O)(CH₂)_nC(O)NH(CH₂)₆NH- (II); wherein n is an integer selected from 12, 14, and 16; said copolyamide has a melting point, as determined with differential scanning calorimetry (DSC) at a scan rate of 10 °C/min in the first heating scan, of at least 280 °C; and the mol % of repeat units are based on the total repeat units present in the copolyamide.

2. The copolyamide of claim 1 having a melting point between 280 °C and

320 °C.

3. The copolyamide of claim 1 consisting essentially of 50 to 60 mol % of a first repeat unit of formula (I) and 40 to 50 mol % of a second repeat unit selected from the group consisting of formula (II).

4. The copolyamide of claim 1 wherein n = 12.

5. The copolyamide of claim 1 wherein n = 14.

6. The copolyamide of claim 1 wherein n = 16.

7. The copolyamide of claim 1 wherein the first repeat unit of formula (I) is

present at 52 to 58 mol % and the second repeat of formula (II) is present at 42 to 48 mol %.

8. The copolyamide of claim 1 wherein 4 mm test bars prepared from said

copolyamide, and immersed in water at a test temperature of 23 °C for a test period of 100 days, has a moisture uptake of less than 2.0 weight percent.

9. The copolyamide of claim 1 , wherein 4 mm test bars prepared from said copolyamide, immersed in water at a test temperature of 23 °C for a test period of 100 days, has a moisture uptake of less than 2.0 weight percent, and a tensile strength retention of at least 70 % as compared to a dry-as-molded control of identical composition.