Polyamide resin and polymerization method and application thereof

Abstract

The invention discloses a polyamide resin, which comprises the following repeating units by mole percentage: a diacid unit: 1,4-cyclohexanedicarboxylic acid; a diamine unit: 1,10-decanediamine and 1,12-dodecanediamine, wherein the amount fraction of 1,10-decanediamine in the diamine is 66-75%. The polyamide resin of the invention is composed of specific repeating units, so that the proportion of the trans structure of the polyamide resin accounts for 77% to 81%, the resin has strong silica gel bonding force, maintains low water absorption, and is suitable for the field of outdoor LED display screens.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to polyamide resin and a polymerization method and application thereof. Background Art

[0002] Compared with the semi-aromatic heat-resistant polyamide polymerized from terephthalic acid or isophthalic acid, the heat-resistant polyamide polymerized from 1,4-cyclohexanedicarboxylic acid monomer does not contain benzene rings in its molecular structure and has a weaker electron-withdrawing effect. Therefore, the heat-resistant polyamide polymerized from 1,4-cyclohexanedicarboxylic acid monomer is less likely to obtain electrons when subjected to long-term ultraviolet aging, and its molecular structure is more stable, and its resistance to ultraviolet aging is better.

[0003] LED encapsulation glue mainly includes epoxy resin and silicone. Silicone has excellent mechanical properties, aging resistance, good thermal stability, weather resistance, flexibility, high light transmittance, low internal stress and low hygroscopicity. Compared with epoxy resin, its performance can better meet the packaging needs of high-power and high-brightness LED products. Therefore, silicone is rapidly replacing epoxy resin and becoming a new generation of more ideal LED packaging materials. With the rapid development of LED, LED lamp beads have begun to be used in the field of outdoor display screens. For outdoor display screen applications, LED lamp beads need to be in high temperature and high humidity environments such as high temperature exposure or rain erosion for a long time. In this case, the water absorption rate of polyamide needs to be reduced, and the reflective bracket composed of polyamide has a strong bonding ability with silicone to prevent water vapor from invading the interior of the lamp bead and causing the lamp bead to fail. However, the high-temperature resistant polyamide based on 1,4-cyclohexanedicarboxylic acid has a low bonding strength with silicone, and there is a problem of separation between plastic and silicone, which makes it impossible to be used in the field of outdoor LED display screens.

[0004] Therefore, how to improve the bonding strength between high temperature resistant polyamide based on 1,4-cyclohexanedicarboxylic acid and silica gel while ensuring a low water absorption rate to meet the needs of the outdoor LED display field is an urgent problem to be solved in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a material having the advantages of high temperature resistance, low water absorption and high bonding strength with silica gel, as well as a polymerization method and application thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] A polyamide resin, measured by mole percentage, comprises the following repeating units:

[0008] Diacid unit: 1,4-cyclohexanedicarboxylic acid;

[0009] Diamine units: 1,10-decanediamine and 1,12-dodecanediamine, wherein the molar fraction of 1,10-decanediamine in the diamines is 66-75%.

[0010] Preferably, the amount of 1,10-decanediamine in the diamine is 69-72%.

[0011] In the high temperature resistant polyamide resin, the trans structure accounts for 77-81% of the amount of the polyamide resin. The test method is: take 5 mg of polyamide resin, dissolve it in 10 mg of deuterated trifluoroacetic acid, and use Bruker's DPX400 nuclear magnetic resonance instrument to perform nuclear magnetic hydrogen spectrum test on the sample. In the nuclear magnetic hydrogen spectrum, the 1.96ppm position is the cis structure peak, and the 1.83ppm position is the trans structure peak. The two peaks are integrated by nuclear magnetic integration to obtain the trans structure ratio of the resin.

[0012] The melting point range of the high temperature resistant polyamide resin is 305-318°C. Referring to ASTM D3418-2003, Standard Test Method for Transition Temperatures of Polymers By Differential Scanning Calorimetry; the specific test method is: using a Perkin Elmer Dimond DSC analyzer to test the melting point of the sample; nitrogen atmosphere, flow rate of 50mL / min; during the test, first heating to 350°C at 20°C / min, maintaining at 350°C for 2min, removing the thermal history of the resin, then cooling to 50°C at 20°C / min, maintaining at 50°C for 2min, and then heating to 350°C at 20°C / min, and setting the endothermic peak temperature at this time as the T melting point.

[0013] The relative viscosity of the high temperature resistant polyamide resin is in the range of 1.8 to 2.8. The test method is to refer to GB12006.1-89 and measure the relative viscosity of polyamide with a concentration of 0.25 g / dl in 98% concentrated sulfuric acid at 25±0.01°C.

[0014] The polymerization method of the high temperature resistant polyamide resin of the present invention comprises the following steps: adding reaction monomers, benzoic acid, sodium hypophosphite and deionized water into a pressure autoclave; the amount of benzoic acid substance is 1.5-3.0% of the amount of reaction monomer substance, the weight of sodium hypophosphite is 0.05-0.15% of the weight of other feed materials except deionized water, and the weight of deionized water is 25-35% of the total feed weight; vacuuming and filling in inert gas (which may be high purity nitrogen) as protective gas, heating to 215-225° C. within 1.5-2.5 hours, and then reacting at this temperature range for 0.5-1.5 hours; then continuing to react at 225-235° C. and 2.0-2.4 MPa pressure for 1-3 hours, removing the water formed during the reaction process, discharging after the reaction is completed, and vacuum drying the prepolymer to obtain a prepolymer product, and the prepolymer product is solid-phase thickened for 8-12 hours under the conditions of 240-260° C. and 45-55 Pa pressure to obtain a polyamide resin.

[0015] The high temperature resistant polyamide resin of the present invention is used for preparing translucent LED related parts, such as LED lamp brackets or LED display screens.

[0016] The present invention has the following beneficial effects

[0017] Through experiments, it was found that the cis / trans structure of the polyamide resin is derived from 1,4-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid constitutes the diacid unit of the polyamide resin of the present invention. By controlling the composition of the diamine unit in the polyamide, it was unexpectedly found that a polyamide resin with a specific trans structure ratio can be obtained (research has found that the trans structure ratio of the polyamide resin in which 1,4-cyclohexanedicarboxylic acid constitutes the diacid unit is related to the structure and ratio of the diamine monomer. The possible reason is that the longer the molecular chain of the diamine monomer, the higher the stability of the trans structure, and therefore the higher the ratio of the trans structure), so that the trans structure of the polyamide resin accounts for 77-81% of the molar fraction of the polyamide resin, so that the polyamide resin of the present invention has a strong silica gel binding force, maintains a low water absorption rate, and is suitable for the field of outdoor LED display screens. Implementation

[0018] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0019] 1,4-Cyclohexanedicarboxylic acid: purity 98%, SKY CHDA, purchased from SK Chemicals;

[0020] 1,10-Decanediamine: purity 97%, D100615, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0021] 1,12-Dodecanediamine: purity 98%, D106441, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0022] 1,6-Hexanediamine: purity 99%, H103910, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0023] 1,14-Tetradecanediamine: purity 95%, SY250668, purchased from Shanghai Shaoyuan Reagent Co., Ltd.;

[0024] Benzoic acid: purity 99.5%, 242381, purchased from Sigma-Aldrich;

[0025] Sodium hypophosphite: purity 98%, S475696, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0026] Embodiment and comparative example The preparation method of high temperature resistant polyamide resin: add reaction monomer, benzoic acid, sodium hypophosphite and deionized water into a pressure autoclave; the amount of benzoic acid substance is 1.5% of the amount of reaction monomer substance, the weight of sodium hypophosphite is 0.10% of the weight of other feed materials except deionized water, and the weight of deionized water is 30% of the total feed weight; evacuate and fill with high-purity nitrogen as protective gas, raise the temperature to 220°C within about 2 hours, and then react for 1 hour within this temperature range; then continue to react for 2 hours at 230°C and a pressure of 2.2 MPa, remove the water formed during the reaction, discharge the material after the reaction is completed, and obtain a prepolymer product after vacuum drying. The prepolymer product is solid-phase thickened for 8-12 hours under the conditions of 250°C and 50Pa pressure to obtain a polyamide resin.

[0027] Various test methods:

[0028] (1) Polyamide relative viscosity test method: refer to GB12006.1-89, polyamide viscosity determination method; the specific test method is: measure the relative viscosity of polyamide with a concentration of 0.25 g / dl in 98% concentrated sulfuric acid at 25±0.01℃.

[0029] (2) Polyamide resin melting point test method: refer to ASTM D3418-2003, Standard Test Method for Transition Temperatures of Polymers By Differential Scanning Calorimetry; the specific test method is: use Perkin Elmer Dimond DSC analyzer to test the melting point of the sample; nitrogen atmosphere, flow rate is 50mL / min; during the test, first increase the temperature to 350℃ at 20℃ / min, keep at 350℃ for 2min to remove the thermal history of the resin, then cool to 50℃ at 20℃ / min, keep at 50℃ for 2min, and then increase the temperature to 350℃ at 20℃ / min, and set the endothermic peak temperature at this time as T melting point.

[0030] (3) Test method for the cis-trans ratio of polyamide: Take 5 mg of polyamide resin, dissolve it in 10 mg of deuterated trifluoroacetic acid, and use Bruker's DPX400 nuclear magnetic resonance instrument to perform nuclear magnetic resonance hydrogen spectrum test on the sample. In the nuclear magnetic hydrogen spectrum, the cis structure peak is at 1.96 ppm, and the trans structure peak is at 1.83 ppm. Perform nuclear magnetic integration of the two peaks to obtain the trans structure ratio of the resin.

[0031] (4) Water absorption rate of polyamide: The sample is injection molded into a 20 mm × 20 mm × 2 mm product, and its weight is recorded as a0. Then it is placed in 95℃ water for 240 hours, and its weight is weighed and recorded as a1. The water absorption rate = (a1-a0) / a0*100%. When the water absorption rate is not higher than 1.5%, it is considered to meet the use requirements.

[0032] (5) Silicone bonding strength: The high-temperature resistant polyamide resin sample was injection molded, and the sample size was 80×20×2.0 mm. Test method: After mixing silicone glue A and silicone glue B in a mass ratio of 1:4, take 0.02g and drop it on one end of the surface of a sample, press the silicone with one end of another sample, and fix it with a clamp. Then put the sample into an oven, pre-cure it at 80°C for 1h, then heat it to 150°C and continue curing for 4h before ending. The cured sample was subjected to a tensile test at a tensile speed of 10 mm / min, and the breaking force was recorded. The present invention characterizes the bonding strength between polyamide and silicone by the breaking force. When the breaking force is not less than 500N, it is considered to meet the use requirements.

[0033] Table 1: Mole percentage content of each unit of polyamide resin in the embodiment and test results

[0034] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 1,4-Cyclohexanedicarboxylic acid 50 50 50 50 50 50 1,10-Decanediamine 33 34.5 35 35.5 36 37.5 1,12-Dodecanediamine 17 15.5 15 14.5 14 12.5 Relative viscosity ηr 2.325 2.316 2.318 2.347 2.356 2.341 Trans structure ratio / mol% 77.2 77.9 78.5 79.3 79.9 80.7 Melting point, °C 305 308 310 312 314 318 Water absorption / % 1.3 1.3 1.3 1.3 1.4 1.4 Breaking force / N 504 536 545 558 549 518

[0035] It can be seen from Examples 1-6 that when 1,10-decanediamine accounts for 69-72% of the molar fraction of the diamine substance, the water absorption rate is lower and the bonding force with silica gel is better.

[0036] Table 2: Mole percentage content of each unit of comparative polyamide resin and test results

[0037] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 1,4-Cyclohexanedicarboxylic acid 50 50 50 50 50 1,10-Decanediamine 32 38.5 36 36 50 1,12-Dodecanediamine 18 11.5 1,6-Hexanediamine 14 1,14-Tetradecanediamine 14 Relative viscosity ηr 2.319 2.372 2.332 2.375 2.361 Trans structure ratio / mol % 76.5 81.6 76.2 83.1 76.2 Melting point, °C 302 322 331 310 351 Water absorption / % 1.3 1.6 2.1 1.4 1.6 Breaking force / N 302 406 287 309 310

[0038] It can be seen from Comparative Example 1 that the molar content of 1,12-dodecanediamine is too high and the trans structure content is too low. Although the water absorption rate is low, the silica gel bonding force is poor.

[0039] It can be seen from Comparative Example 2 that the trans structure content is not within the scope of the present invention, the binding force with silica gel is low, and the water absorption rate is high.

[0040] It can be seen from Comparative Examples 3-5 that it is difficult for other types of monomers to achieve a trans-structure ratio within the scope of the present invention, and it is difficult to simultaneously achieve the characteristics of low water absorption and high bonding strength with silica gel.

[0041] The water absorption rate of the polyamide resin of the present invention is less than or equal to 1.4%, and the tensile strength in the test of silica gel bonding strength is greater than 500N.

Claims

1. A polyamide resin, characterized in that: In terms of molar percentage, the composition of the repeating unit is: Diacid unit: 1,4-cyclohexanedicarboxylic acid; Diamine units: 1,10-decanediamine and 1,12-dodecanediamine, of which 1,10-decanediamine accounts for 71-72% of the diamine substance; In the polyamide resin, the trans structure ratio is 79.3-79.9%.

2. The polyamide resin according to claim 1, characterized in that The melting point of the polyamide resin is in the range of 305-318°C.

3. The polyamide resin according to claim 1, characterized in that The relative viscosity of the polyamide resin is in the range of 1.8-2.

8. The test method is to refer to GB12006.1-89 and measure the relative viscosity of the polyamide with a concentration of 0.25 g / dl in 98% concentrated sulfuric acid at 25±0.01°C.

4. The polymerization method of the polyamide resin according to any one of claims 1 to 3, characterized in that: The following steps are involved: Add reaction monomers, benzoic acid, sodium hypophosphite and deionized water into a pressure autoclave; the amount of benzoic acid is 1.5-3.0% of the total amount of reaction monomers, the weight of sodium hypophosphite is 0.05-0.15% of the weight of other materials except deionized water, and the weight of deionized water is 25-35% of the total weight of materials; evacuate and fill with inert gas as protective gas, raise the temperature to 215-225° C. within 1.5-2.5 hours under stirring, then react at this temperature range for 0.5-1.5 hours, and then continue to react at 225-235° C. and a pressure of 2.0-2.4 MPa for 1-3 hours, remove the water formed during the reaction, discharge the material after the reaction is completed, and obtain a prepolymer product after vacuum drying the prepolymer, and solid phase thicken the prepolymer product for 8-12 hours under the conditions of 240-260° C. and a pressure of 45-55 Pa to obtain a polyamide resin.

5. The use of the polyamide resin according to any one of claims 1 to 3, characterized in that: Used to prepare translucent LED related components.

6. Application of the polyamide resin obtained by the preparation method of claim 4, characterized in that: Used to prepare translucent LED related components.