WO2022127249A1 - Polyamide molding composition, preparation method therefor, and application thereof - Google Patents

Abstract

Disclosed are a polyamide molding composition, a preparation method therefor, and an application thereof. The polyamide molding composition comprises the following components: 100 parts polyamide resin, 4-10 parts hyperbranched polyamide, and 0-100 parts of a reinforcing filler. The polyamide resin is selected from any one of PA10T or PA10T/10I. In the present invention, by means of adding a specific amount of amino-terminated hyperbranched polyamide to a polyamide material, a polyamide molding composition that has a low crystallization temperature, a slow crystallization speed and low water absorption is prepared. The polyamide molding composition of the present invention can delay the cooling rate of material in a mold under cold molding conditions in multiple mold cavities, thus improving the mold filling fluidity of the material, such that the material can better replicate the mold structure to avoid the problem of short shots and bareness, thereby increasing the air tightness of products. The polyamide molding composition can be applied to the field of LED display reflective brackets.

Description

A kind of polyamide molding composition and its preparation method and application technical field

The invention relates to the technical field of engineering plastics, in particular to a polyamide molding composition and a preparation method and application thereof.

Background technique

Because of its good mechanical properties, wear resistance, chemical resistance and self-lubrication, and low coefficient of friction, polyamides are widely suitable for filling and reinforcing with glass fibers and other fillers. However, common polyamides such as PA6 and PA66 usually have a melting point below 260°C and lack high temperature resistance, so they cannot be used in areas with higher operating temperatures. In recent years, semi-aromatic polyamides have been mainly developed due to their low water absorption and high temperature resistance.

LED reflective brackets need to undergo high-temperature processing such as reflow soldering process, requiring materials with high thermal deformation temperature and melting point; a series of semi-aromatic polyamides such as PA10T, PA9T and PA6T copolymers have become mainstream materials for LED reflective brackets . As consumers' demand for LED display resolution increases, the size of LED lamp beads gradually decreases, and the LED reflective bracket gradually develops in the direction of small size and thin wall; in order to improve production efficiency and reduce production energy consumption, injection molding factories gradually use LED The number of mold cavities of the reflective bracket is increased from less than 1000 to more than 2000, and cold molding is used instead of high mold temperature molding. For the LED display reflective bracket, it is required to have good air tightness. Therefore, under the existing injection molding conditions of multi-cavity and cold molding, the material needs to have a lower crystallization temperature and a slower crystallization rate, slowing down the material's crystallization. Cooling speed, so as to ensure that the material has good filling fluidity during injection molding, avoid the problem of under-injection and lack of glue, and improve the air tightness of the part. Although the existing material based on PA6T copolymer has a relatively slow crystallization rate, its water absorption rate is relatively high. After the material absorbs water, it will cause dimensional changes and a decrease in mechanical strength, resulting in poor air tightness of the product; while PA10T copolymerization Although the water absorption rate is low, it has a high crystallization temperature, a fast crystallization rate, and rapid crystallization during injection molding, which is prone to problems of under injection and lack of glue, resulting in poor air tightness of the parts.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a polyamide molding composition with low crystallization temperature, slow crystallization speed and low water absorption rate.

Another object of the present invention is to provide a process for the preparation of the above-mentioned polyamide molding composition.

The present invention is achieved through the following technical solutions:

100 parts of polyamide resin;

Hyperbranched polyamide 4-10 parts;

Reinforcing filler 0～100 copies;

The polyamide resin is selected from any one of PA10T or PA10T/10I.

The polyamide resin of the present invention is formed by polycondensation of diamine and diacid; the molar fraction of terephthalic acid in the diacid in the polyamide resin is 90% to 100%.

The polyamide resin of the present invention can be commercially available, or can be prepared by the following conventional polymerization methods, specifically: in a pressure kettle equipped with a magnetic coupling stirring, a condenser tube, a gas phase port, a feeding port, and a pressure explosion-proof port Add diamine and diacid according to the proportion; then add benzoic acid, catalyst sodium hypophosphite and deionized water; the amount of benzoic acid is 1.0%～3.0% of the total amount of decanediamine and diacid, the weight of sodium hypophosphite In order to remove 0.1% to 0.3% of the weight of other materials except ionized water, the weight of deionized water is 20% to 40% of the total weight of the materials; vacuumize and fill with high-purity nitrogen as protective gas, and heat up to 220 in 2 hours under stirring. ℃～230 ℃, the reaction mixture is stirred for 1 hour, and then the temperature of the reactant is raised to 240 ℃～250 ℃ under stirring; The reaction is continued for 1 to 3 hours under constant temperature and constant pressure, by removing the water formed While keeping the pressure constant, after the reaction is completed, the material is discharged, and the prepolymer is vacuum-dried at 80° C. for 24 hours to obtain a prepolymerized product. 6 to 12 hours to obtain a polyamide resin.

The purpose of the present invention is to modify the polyamide resin, so the present invention does not require the specification parameters of the polyamide resin. Generally, the relative viscosity of the polyamide resin used for the LED reflective bracket is 2.0 to 2.4; the relative viscosity is measured by the concentration of 0.25g/dL of polyamide in 98% concentrated sulfuric acid at 25±0.01°C. Test The method refers to the standard GB12006.1-89.

It is found through research in the present invention that adding a certain amount of hyperbranched polyamide containing terminal amino groups can significantly reduce the crystallization temperature and crystallization rate of the polyamide composition. The molecule of hyperbranched polyamide contains multiple amino groups, which can react with the carboxyl groups at the ends of multiple polyamide molecular chains to connect into the polyamide molecular chain to form a branched structure; when the content of the branched structure reaches a certain amount, It will destroy the regularity of the molecular chain structure, thereby reducing the crystallization temperature and slowing down the crystallization rate.

Preferably, in parts by weight, the hyperbranched polyamide is 5 to 9 parts.

The terminal amino group of the hyperbranched polyamide of the present invention is 3-16 mol/mol, and the number average molecular weight is 350-2200 g/mol. The content of terminal amino groups is too low to react with a sufficient number of polyamide molecular chain ends, resulting in limited effect of destroying the regularity of the molecular chain; The composition as a whole was thermoset and could not be processed. Preferably, the terminal amino group of the hyperbranched polyamide is 7-9 mol/mol, and the number average molecular weight is 800-1000 g/mol.

The reinforcing filler is selected from at least one of fibrous reinforcing fillers or non-fibrous reinforcing fillers. Specifically, the fibrous reinforcing filler is selected from glass fibers, potassium titanate fibers, metal-clad glass fibers, ceramic fibers, wollastonite fibers, metal carbide fibers, metal solidified fibers, asbestos fibers, alumina fibers , at least one of silicon carbide fibers, gypsum fibers or boron fibers, aramid fibers or carbon fibers; the non-fibrous reinforcing filler is selected from potassium titanate whiskers, zinc oxide whiskers, aluminum borate whiskers, Wollastonite, zeolite, sericite, kaolin, mica, talc, clay, pyrophyllite, bentonite, montmorillonite, hectorite, synthetic mica, asbestos, aluminosilicate, alumina, silica, magnesia, oxide Zirconium, titanium oxide, iron oxide, calcium carbonate, magnesium carbonate, dolomite, calcium sulfate, barium sulfate, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, glass beads, ceramic beads, boron nitride, silicon carbide, or dioxide One or more of silicon.

According to material performance requirements, the polyamide molding composition of the present invention, in parts by weight, further includes 0-1 part of an auxiliary agent; the auxiliary agent includes an antioxidant; specifically, the antioxidant is N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide);

The polyamide molding composition of the present invention further comprises 0 to 40 parts by weight of a pigment. It is often necessary to add a certain amount of pigments to the LED reflector to enhance the reflection effect. However, in the examples and comparative examples of the present application, the pigment is used as a means of characterization, and whether or not the pigment is added cannot be used as a limitation on the technical solution of the present invention.

The pigment is titanium dioxide surface-treated with polysiloxane; other types of pigments can also be selected according to requirements.

The present invention also provides a method for preparing the above-mentioned polyamide molding composition, which includes the following steps: mixing the components uniformly according to the proportion, melt-blending, extruding and pelletizing through a twin-screw extruder to obtain a polyamide mold plastic composition; wherein, the temperature of the twin-screw extruder is set at 280-340°C.

The present invention also provides the application of the above-mentioned polyamide molding composition in the field of LED display screen reflective brackets.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention prepares a polyamide molding composition with low crystallization temperature, slow crystallization speed (large half-height width of crystallization peak) and low water absorption by adding a specific amount of amino-terminated hyperbranched polyamide into the polyamide material. Under the condition of cold molding with the number of cavities, the cooling rate of the material in the mold can be delayed, the filling fluidity of the material can be improved, the material can better replicate the mold structure, avoid the problems of under-injection and lack of glue, and then improve the parts. air tightness.

The polyamide molding composition of the present invention has a melting point of 305-320°C, good heat resistance and suitable melt processing temperature, while the crystallization temperature is lower than 265°C, and the crystallization peak width at half maximum is greater than 16°C; Below 0.45%, the injection molded parts have good air tightness and can meet the strict air tightness requirements of the LED display reflective bracket.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Now the used raw materials of embodiment and comparative example are described as follows, but are not limited to these materials:

Diamine: 1,10-decanediamine, commercially available;

Diacids: terephthalic acid, isophthalic acid, commercially available;

Hyperbranched polyamide 1: HyPer N101, Wuhan Hyperbranched Resin Technology Co., Ltd., terminal amino group 3～4mol/mol, molecular weight 350～370g/mol;

Hyperbranched polyamide 2: HyPer N102, Wuhan Hyperbranched Resin Technology Co., Ltd., terminal amino group 7～9mol/mol, molecular weight 800～1000g/mol;

Hyperbranched polyamide 3: HyPer N103, Wuhan Hyperbranched Resin Technology Co., Ltd., terminal amino group 12～16mol/mol, molecular weight 1900～2200g/mol;

Hyperbranched polyamide 4: HyPer HPN202, Wuhan Hyperbranched Resin Technology Co., Ltd., terminal hydroxyl group 12mol/mol, molecular weight 2700g/mol;

Reinforcing material: glass fiber, commercially available;

Pigment: titanium dioxide, commercially available;

Antioxidant: N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide), commercially available.

The preparation method of polyamide resin: add diamine and diacid according to the ratio of Table 1 in a pressure kettle equipped with magnetic coupling stirring, condenser tube, gas phase port, feeding port and pressure explosion-proof port; then add benzoic acid, catalyst sodium hypophosphite and deionized water; the amount of benzoic acid material is 2.5% of the amount of diamine and diacid total material, and the weight of sodium hypophosphite is 0.1% of the weight of other feeds except ionized water, and the weight of deionized water is 30% of the total feed weight. %; vacuumed and filled with high-purity nitrogen as protective gas, heated to 220°C within 2 hours under stirring, stirred the reaction mixture for 1 hour, and then raised the temperature of the reactant to 240°C under stirring; Continue for 2 hours under constant pressure, keep the pressure constant by removing the water formed, discharge after completion of the reaction, and vacuum dry the prepolymer at 80° C. for 24 hours to obtain a prepolymerized product, the prepolymerized product is at 250 °C. ℃ and 50Pa vacuum conditions were solid-phase tackified for 10 hours to obtain a polyamide resin.

The preparation method of the polyamide molding composition of Examples and Comparative Examples: according to the proportions in Table 2 and Table 3, the components were mixed uniformly, melt-blended, extruded and pelletized by a twin-screw extruder to obtain polyamide A molding composition; wherein the temperature of the twin-screw extruder is set at 280-340°C.

Test methods or standards for each performance:

(1) Relative viscosity of polyamide resin: the test method refers to GB12006.1-89, the relative viscosity measured by polyamide with a concentration of 0.25g/dL in 98% concentrated sulfuric acid at 25±0.01°C.

(2) Melting point, crystallization temperature and crystallization peak width at half maximum of polyamide composition: refer to ASTM _D3418-2003 , Standard Test Method for Transition Temperatures of Polymers By Differential Scanning Calorimetry; Temperature T _c , crystallization peak width at half maximum ΔT _1/2 ; the smaller the crystallization peak width at half maximum, the faster the crystallization rate; the larger the crystallization peak width at half maximum, the slower the crystallization rate.

(3) Water absorption rate of polyamide composition: test according to GB/T 1034-2008 Method 1, inject the polyamide composition into a rectangular plate of 84mm*54mm*2.0mm, dry at 50±2°C for 24h, Then soak in water at 23±2°C for 24h, test the mass change of the sample strip, water absorption %=(mass after soaking-mass before soaking)/mass before soaking*100.

(4) Air tightness test: put the obtained polyamide composition in an oven at 120°C for 4 hours, and then use Toyo CS-100 injection molding machine for injection molding; LED bracket model 2121, number of mold cavities 1440; Cooling with cooling water; take 20 obtained LED brackets and encapsulate them with silica gel to obtain LED lamp beads; immerse the obtained LED lamp beads into a detection liquid of 1 volume part of red ink and 1 volume part of alcohol (purity 90%-98%). medium; heat and boil for 4 hours, take out the LED lamp bead, observe the color of the LED lamp bead, if no red seeps into the inside of the lamp bead, it means that the LED lamp bead has good air tightness, marked as O; there is at least one red seepage into the inside of the lamp bead It means that the air tightness of the LED lamp bead is poor, denoted as X.

Table 1: The ratio of each monomer of polyamide resin PA10T/10I

	PA 1	PA 2	PA3	PA4
1,10-Decanediamine/mol	20	20	20	20
terephthalic acid/mol	20	19	18	17
isophthalic acid/mol		1	2	3
Relative viscosity	2.213	2.221	2.215	2.222

Table 2: The specific proportions (parts by weight) of each component of Examples 1 to 8 and the test results of each performance

Table 3: The specific proportions (parts by weight) of the components of Comparative Examples 1 to 7 and the test results of each performance

From the results of the above examples and comparative examples, it can be seen that the required proportions of the components in the present invention have a low crystallization temperature, a fast crystallization rate, and a low water absorption rate of the prepared polyamide composition. The air tightness of the lamp beads is qualified.

Comparative example 1, the amount of hyperbranched polyamide added is too small, although the water absorption rate is low, but the crystallization temperature of the polyamide composition is increased, the crystallization peak width at half maximum is reduced, the material is rapidly crystallized during injection molding, and the mold is filled. The fluidity is poor, and there will be problems of under injection and lack of glue, and the air tightness of the injection molded LED lamp beads is poor.

Comparative example 2, the addition amount of hyperbranched polyamide is too much, although crystallization peak half-height width is larger, but the melting point of polyamide composition rises sharply, causes melt processing difficulty, and crystallization temperature is high, water absorption is larger, injection molding. The resulting LED lamp beads have poor air tightness.

Comparative example 3/4/5, without adding hyperbranched polyamide, although the water absorption rate is low, the crystallization temperature is high, the crystallization peak width at half maximum is small, the material is rapidly crystallized during injection molding, and the mold filling fluidity is poor. Due to the lack of glue, the air tightness of the injection-molded LED lamp beads is unqualified.

Compared with Example 4, Comparative Example 6 shows that the mole fraction of terephthalic acid in diacid is less than 90 mol%. Although the obtained polyamide composition has a lower crystallization temperature and a larger crystallization peak width at half maximum, its The melting point is lowered to below 300°C, the heat resistance is poor, and the water absorption rate is high, resulting in poor air tightness of the injection molded LED lamp beads.

Comparative Example 7, the addition of hydroxyl-terminated hyperbranched polyester has no effect on reducing the crystallization temperature and crystallization rate of the material. The crystallization temperature of the polyamide composition is high, the crystallization peak width at half maximum is small, and the air tightness of the injection molded LED lamp beads is not good. qualified.

Claims (10)

1. A polyamide molding composition, characterized in that, in parts by weight, it comprises the following components:

   100 parts of polyamide resin;

   Hyperbranched polyamide 4 to 10 parts;

   Reinforcing filler 0～100 copies;

   The polyamide resin is selected from any one of PA10T or PA10T/10I.
2. The polyamide molding composition according to claim 1, wherein the molar fraction of terephthalic acid in the diacid in the polyamide resin is 90% to 100%.
3. The polyamide molding composition according to claim 1, wherein the relative viscosity of the polyamide resin is 2.0-2.4.
4. The polyamide molding composition according to claim 1, characterized in that, in parts by weight, the hyperbranched polyamide is 5-9 parts by weight.
5. The polyamide molding composition according to claim 1, wherein the terminal amino group of the hyperbranched polyamide is 3-16 mol/mol, and the number average molecular weight is 350-2200 g/mol.
6. The polyamide molding composition according to claim 5, wherein the terminal amino group of the hyperbranched polyamide is 7-9 mol/mol, and the number average molecular weight is 800-1000 g/mol.
7. The polyamide molding composition according to claim 1, wherein the reinforcing filler is selected from at least one of a fibrous reinforcing filler or a non-fibrous reinforcing filler; the fibrous reinforcing filler is selected from Glass fibers, potassium titanate fibers, metal-clad glass fibers, ceramic fibers, wollastonite fibers, metal carbide fibers, metal-cured fibers, asbestos fibers, alumina fibers, silicon carbide fibers, gypsum fibers or boron fibers, aromatic fibers At least one of polyamide fibers or carbon fibers; the non-fibrous reinforcing filler is selected from potassium titanate whiskers, zinc oxide whiskers, aluminum borate whiskers, wollastonite, zeolite, sericite, kaolin, mica , talc, clay, pyrophyllite, bentonite, montmorillonite, hectorite, synthetic mica, asbestos, aluminosilicate, alumina, silica, magnesia, zirconia, titania, iron oxide, calcium carbonate, carbonic acid One or more of magnesium, dolomite, calcium sulfate, barium sulfate, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, glass beads, ceramic beads, boron nitride, silicon carbide or silicon dioxide.
8. The polyamide molding composition according to claim 1, characterized in that, in parts by weight, it further comprises 0-1 part of an auxiliary agent; 0-40 parts of a pigment; and the auxiliary agent comprises an antioxidant.
9. The method for preparing a polyamide molding composition according to any one of claims 1 to 8, characterized in that it comprises the following steps: mixing the components uniformly according to the proportion, and melt-blending them through a twin-screw extruder. , extrusion and granulation to obtain a polyamide molding composition; wherein, the temperature of the twin-screw extruder is set to 280-340°C.
10. Application of the polyamide molding composition according to any one of claims 1 to 8 in the field of LED display screen reflective brackets.