Prime-coat-free low-shrinkage PBT (polybutylene terephthalate) alloy material and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer materials, and discloses a prime coat-free low-shrinkage PBT (polybutylene terephthalate) alloy material and a preparation method thereof. The composite material is prepared from the following raw materials in parts by weight: 38.6 to 50.5 parts of polybutylene terephthalate resin, 15 to 20 parts of acrylonitrile-butadiene-styrene copolymer, 10 to 15 parts of acrylonitrile-styrene-acrylate copolymer, 0.2 to 0.5 part of main antioxidant, 0.2 to 0.5 part of auxiliary antioxidant, 0.5 to 2.0 parts of compatilizer, 10 to 15 parts of glass fiber, 5 to 10 parts of mineral powder, 1.0 to 3.0 parts of lubricant and 1.0 to 2.0 parts of black additive. The PBT resin is modified, the ABS resin and the ASA resin are added, the rigidity and the surface hardness of the material are improved, the shrinkage rate of the material is reduced through combination of the glass fibers and the mineral powder, and the PBT alloy has the good prime coat-free characteristic due to the proper proportion of the materials. After the PBT alloy material obtained by the invention is further subjected to injection molding processing, the dual effects of no prime coat and low shrinkage of the material can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a low-shrinkage PBT alloy material without primer. Background Art

[0002] Polybutylene terephthalate (PBT) is a semi-crystalline polymer with excellent electrical properties, chemical corrosion resistance, heat resistance, low water absorption and easy processing. It began industrial production in the last century. Although it started the latest among engineering plastics, it is one of the varieties with the fastest development speed. PBT alloy materials are made by blending PBT with other polymers or adding specific additives. It combines the excellent properties of PBT and the advantages of other components, such as good heat resistance, mechanical properties, electrical insulation and chemical stability, etc., and occupies an important position in the field of engineering plastics. However, unmodified PBT materials have some defects, such as a large molding shrinkage rate, which will cause the size of the product to be unstable during the molding process, and problems such as warping and deformation are likely to occur, affecting the accuracy and assembly performance of the product; at the same time, its surface properties also need to be improved, such as insufficient surface gloss and insufficient adhesion to coatings, etc., which requires primer treatment to improve.

[0003] At present, although certain progress has been made in the modification research of PBT materials, there are still deficiencies in achieving the balance between primer-free and low shrinkage. For example, the prior art CN109401221A discloses a weather-resistant low-warpage glass fiber-reinforced PBT / AS / ASA material and its preparation method. The composite material prepared by this technology has a relatively high shrinkage rate and more surface defects. A higher glass fiber content may also cause the appearance of the floating phenomenon. This is because with the increase in the glass fiber content, during the injection molding process of the composite material, the glass fiber exerts a restraining effect on the surrounding resin matrix, restricting the shrinkage of the material. However, too much glass fiber makes a small amount of glass fiber float on the surface of the composite material, resulting in poor appearance and surface defects of the composite material, and complex surface treatment is required before painting. Some studies focus on improving the mechanical properties of the material or improving a single surface property, rather than comprehensively considering the synergistic improvement of these two key properties of primer-free and low shrinkage. For example, some methods of reducing the shrinkage rate by adding fillers may cause the surface properties of the material to deteriorate and require further primer treatment; while some methods of improving the surface properties may have an adverse effect on the shrinkage rate of the material and cannot effectively solve the problem of molding shrinkage.

[0004] Therefore, how to provide a low-shrinkage PBT alloy material without primer and its preparation method, so that the PBT alloy has both a low shrinkage rate and is primer-free, is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a primerless low-shrinkage PBT alloy material and a preparation method thereof.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows:

[0007] A primerless low-shrinkage PBT alloy material, the raw material composition includes the following components by weight: 38.6-50.5 parts of polybutylene terephthalate resin (PBT), 15-20 parts of acrylonitrile-butadiene-styrene copolymer (ABS), 10-15 parts of acrylonitrile-styrene-acrylate copolymer (ASA), 0.2-0.5 part of a primary antioxidant, 0.2-0.5 part of a secondary antioxidant, 0.5-2.0 parts of a compatibilizer, 10-15 parts of glass fiber, 5-10 parts of mineral powder, 1.0-3.0 parts of a lubricant, and 1.0-2.0 parts of a black additive.

[0008] The intrinsic viscosity of the above polybutylene terephthalate resin (PBT) is 0.8-1.2 dL / g. The polybutylene terephthalate resin with an intrinsic viscosity in the range of 0.8-1.2 dL / g helps to ensure that the PBT molecular chain length is moderate, enabling it to better interact with other components in the alloy and further enhancing the impact resistance.

[0009] The content of butadiene in the above acrylonitrile-butadiene-styrene copolymer is 10-30%, and the content of acrylonitrile in the acrylonitrile-styrene-acrylate copolymer is 20-30%. The rubber phase content in ABS is 10-30% to provide good toughness; when the butadiene content in ABS is too high, it will lead to toughness contradictions, mechanical property degradation, and processing problems due to excessive rubber phase. At the same time, considering the copolymer monomer ratio in ASA (acrylonitrile 20-30%) to optimize the overall formula and ensure the balance of comprehensive properties such as primerless, low shrinkage, and high toughness of the PBT alloy. The content of acrylonitrile in ASA is 20-30%, which helps to improve the rigidity and surface hardness of the material. Its epoxy group can react with the terminal carboxyl and terminal hydroxyl groups of PBT, enhancing the compatibility between PBT and ABS / ASA, reducing the phase separation phenomenon, and improving the overall uniformity of the material; when the acrylonitrile content in ASA is too high, it will lead to increased brittleness, aggravated phase separation, and deteriorated processing performance due to excessive rigidity. At the same time, considering formula optimization (such as introducing a toughening agent or compatibilizer) to make up for the possible negative impacts brought by high acrylonitrile and ensure the synergistic improvement of comprehensive properties such as primerless, low shrinkage, and high rigidity of the PBT alloy.

[0010] The above mineral powder is at least one of talc powder, mica powder and kaolin. The glass fiber is an alkali-free chopped glass fiber with a length of 3-6 mm and a diameter of 10-15 μm, and is treated with a silane coupling agent. The surface treatment of the glass fiber is carried out with a silane coupling agent to enhance the bonding force between the filler and the matrix. After adding the mineral powder to the main material, the mineral powder can serve as a dispersion medium, making the glass fiber more evenly distributed in the alloy material, helping to form a uniform surface, reducing surface defects, enabling the coating to adhere more evenly to the material surface, eliminating the need for a primer to compensate for surface differences, and the mineral powder has a certain rigidity and filling effect. Adding the mineral powder first can fill the voids between the polymer molecular chains and restrict the movement of the molecular chains. The glass fiber, mineral powder and matrix can form a tight bonding network, further enhancing the internal structural stability of the material. This synergistic effect causes the shrinkage of the molecular chains to be more restricted during the cooling and curing process of the material, thus effectively reducing the shrinkage rate of the material.

[0011] The above main antioxidant includes at least one of pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; the co-antioxidant is at least one of tris(2,4-di-tert-butylphenyl) phosphite and bis(2,4-dicumylphenyl) pentaerythritol diphosphite.

[0012] The above compatibilizer is a terpolymer random copolymer of styrene-acrylonitrile-glycidyl methacrylate (SAG) or ethylene-methyl acrylate-glycidyl methacrylate copolymer (E-MA-GMA).

[0013] The above lubricant is one or a mixture of two of pentaerythritol stearate and ethylene bisstearamide (EBS).

[0014] The above black additive is at least one of an AS carrier black masterbatch and a carbon black masterbatch.

[0015] The preparation method of the above primer-free low shrinkage rate PBT alloy material is as follows:

[0016] (1) Dry the polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer and acrylonitrile-styrene-acrylate copolymer in an oven at 80-100 °C for 4-6 h;

[0017] (2) According to the weight parts, mix the dried polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene-acrylate copolymer, main antioxidant, co-antioxidant, compatibilizer, mineral powder, lubricant and black additive evenly to obtain a premix;

[0018] (3) The premix obtained in step (2) and glass fiber are melt-extruded, pelletized, and sieved to obtain a primerless low shrinkage PBT alloy material.

[0019] Furthermore, the temperatures of each section of the above melt extrusion are: 225 - 235 °C for sections 2 - 4, 220 - 235 °C for sections 5 - 8, 220 - 230 °C for sections 9 - 10, and 220 - 230 °C for the die head.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) For the primerless low shrinkage PBT alloy material provided by the present invention, the intrinsic viscosity of the polybutylene terephthalate resin is in the range of 0.8 - 1.2 dL / g, which helps to ensure that the PBT molecular chain length is moderate, enabling it to interact better with other components in the alloy and further enhancing the impact resistance. The rubber phase content in ABS is 10% - 30% to provide good toughness. The acrylonitrile content in ASA is 20% - 30%, which helps to improve the rigidity and surface hardness of the material. Its epoxy group can react with the terminal carboxyl group and terminal hydroxyl group of PBT, enhancing the compatibility between PBT and ABS / ASA, reducing the phase separation phenomenon, and improving the overall uniformity of the material. The glass fiber surface is treated with a silane coupling agent to enhance the bonding force between the filler and the matrix. After adding mineral powder to the main materials, the mineral powder can act as a dispersion medium, making the glass fiber more evenly distributed in the alloy material, helping to form a uniform surface, reducing surface defects, enabling the coating to adhere more evenly to the material surface, eliminating the need for a primer to compensate for surface differences, and the mineral powder has a certain rigidity and filling effect. Adding the mineral powder first can fill the voids between the polymer molecular chains, restricting the movement of the molecular chains. The glass fiber, mineral powder, and matrix can form a tight bonding network, further enhancing the internal structural stability of the material. This synergistic effect enables the shrinkage of the molecular chains to be more restricted during the cooling and curing process of the material, thereby effectively reducing the shrinkage rate of the material. The lubricant can improve the processing fluidity of the material, reduce the melt viscosity, make the material easier to form during processing, and at the same time reduce the defects on the surface of the product. The compatibilizer can effectively enhance the interfacial bonding force between PBT, ABS, and ASA, promote the uniform dispersion of each component, and improve the comprehensive performance of the alloy material.

[0022] (2) Mineral powder (one or more combinations of talc powder, mica powder, kaolin) and glass fiber are added step by step in a certain proportion. The initially added mineral powder can, to a certain extent, adjust the surface structure of the material, enabling the coupling agent-coated glass fiber to better play its role, thereby enhancing the physical adsorption and chemical bonding between the coating and the alloy material, achieving the effect of eliminating the need for a primer. Moreover, the step-by-step addition of mineral powder and glass fiber containing a coupling agent helps improve the thermal conductivity within the material. The thermal conductivity of the mineral powder is different from that of the polymer matrix, and it can form thermal conduction channels in the material, enabling heat to be transferred more evenly. The good bonding between the glass fiber containing a coupling agent and the matrix is also conducive to heat transfer. Uniform thermal conduction can reduce the problem of inconsistent shrinkage caused by temperature differences within the material and lower the overall shrinkage rate. On the other hand, the appropriate weight ratio of glass fiber to mineral powder and the specific length and diameter range of the glass fiber enable the filler to have good fluidity and dispersibility during the mixing process. This ratio and size range can prevent mixing difficulties caused by excessive filler and ensure that the filler forms an effective reinforcement and filling structure within the material. Brief Description of the Drawings

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a flowchart for preparing a primerless low-shrinkage PBT alloy material of the present invention. Detailed Embodiments

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present invention pertains. In case of conflict, this specification shall prevail.

[0027] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or by existing methods.

[0028] A kind of primerless low-shrinkage PBT alloy material provided by the present application, by weight, comprises the following components: 38.6-50.5 parts of polybutylene terephthalate resin, 15-20 parts of acrylonitrile-butadiene-styrene copolymer (ABS), 10-15 parts of acrylonitrile-styrene-acrylate copolymer (ASA), 0.2-0.5 part of a primary antioxidant, 0.2-0.5 part of a secondary antioxidant, 0.5-2.0 parts of a compatibilizer, 10-15 parts of glass fiber, 5-10 parts of mineral powder, 1.0-3.0 parts of a lubricant, and 1.0-2.0 parts of a black additive.

[0029] Among them, the intrinsic viscosity of the polybutylene terephthalate resin is in the range of 0.8-1.2 dL / g; the rubber phase (butadiene) content in the ABS is 10%-30%, and the acrylonitrile content in the ASA is 20%-30%.

[0030] For a primerless low-shrinkage PBT alloy material provided by the present invention, the intrinsic viscosity of the polybutylene terephthalate resin is in the range of 0.8-1.2 dL / g, which helps to ensure that the PBT molecular chain has a moderate length, enabling it to better interact with other components in the alloy and further enhancing the impact resistance. The rubber phase content in the ABS is 10%-30% to provide good toughness, and the acrylonitrile content in the ASA is 20%-30%, which helps to improve the rigidity and surface hardness of the material. Its epoxy group can react with the terminal carboxyl and terminal hydroxyl groups of PBT, enhancing the compatibility between PBT and ABS / ASA, reducing the phase separation phenomenon, and improving the overall uniformity of the material. The glass fiber surface is treated with a silane coupling agent to enhance the bonding force between the filler and the matrix. After adding the mineral powder to the main materials, the mineral powder can act as a dispersion medium, making the glass fiber more evenly distributed in the alloy material, helping to form a uniform surface, reducing surface defects, enabling the coating to adhere more evenly to the material surface, eliminating the need for a primer to compensate for surface differences, and the mineral powder has a certain rigidity and filling effect. Adding the mineral powder first can fill the voids between the polymer molecular chains, restricting the movement of the molecular chains. The glass fiber, mineral powder, and matrix can form a tight bonding network, further enhancing the internal structural stability of the material. This synergistic effect enables the molecular chain shrinkage to be more restricted during the cooling and curing process of the material, thereby effectively reducing the shrinkage rate of the material. The lubricant can improve the processing fluidity of the material, reduce the melt viscosity, make the material easier to mold during the processing, and at the same time reduce the defects on the surface of the product. The compatibilizer can effectively enhance the interfacial bonding force between PBT, ABS, and ASA, promote the uniform dispersion of each component, and improve the comprehensive performance of the alloy material.

[0031] In some possible embodiments, the mineral powder is one or a combination of talc powder, mica powder, and kaolin, and the glass fiber is an alkali-free chopped glass fiber with a length of 3-6 mm and a diameter of 10-15 μm. After the glass fiber is surface-treated with a silane coupling agent, the interfacial bonding force between the filler and the resin matrix can be enhanced. One end of the silane coupling agent can react with active groups such as hydroxyl groups on the surface of the filler, and the other end can form a chemical bond or physical adsorption with the resin matrix. This enables the glass fiber to disperse better in the alloy material and bind tightly to the matrix, reducing interfacial defects. This good interfacial bonding helps to improve the surface quality of the material, making the material surface smoother and flatter, providing a good basis for the surface treatment without primer. The mineral powder (one or a combination of talc powder, mica powder, and kaolin) and the glass fiber are added step by step in a certain proportion. The mineral powder added first can adjust the surface structure of the material to a certain extent, enabling the coupling agent-treated glass fiber to play a better role, thereby enhancing the physical adsorption and chemical bonding between the coating and the alloy material and achieving the effect of primer-free. Moreover, the step-by-step addition of the mineral powder and the coupling agent-treated glass fiber helps to improve the thermal conductivity of the material. The thermal conductivity of the mineral powder is different from that of the polymer matrix, and it can form a thermal conduction channel in the material to make the heat transfer more uniform. The good bonding between the coupling agent-treated glass fiber and the matrix is also conducive to heat transfer. Uniform thermal conduction can reduce the problem of inconsistent shrinkage caused by temperature differences inside the material and reduce the overall shrinkage rate. On the other hand, the appropriate weight ratio of the glass fiber to the mineral powder and the specific length and diameter range of the glass fiber enable the filler to have good fluidity and dispersibility during the mixing process. This ratio and size range can prevent mixing difficulties caused by excessive filler and ensure that the filler forms an effective reinforcement and filling structure in the material. The glass fiber in the alloy material can limit the shrinkage of PBT, ABS, and ASA resins during the cooling process. Due to the low coefficient of thermal expansion of the glass fiber itself, during the process of the material cooling from the molten state to the solid state, it can exert a restraining effect on the surrounding resin matrix, reducing volume shrinkage, thereby effectively reducing the shrinkage rate of the alloy material and improving the dimensional accuracy of the product. The mineral powder also makes a positive contribution to reducing the shrinkage rate. The addition of the mineral powder can change the crystallization behavior of the material and the stacking mode of the molecular chains, making the structure of the material more stable and further reducing the shrinkage phenomenon.

[0032] In some possible embodiments, the primary antioxidant includes at least one of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine, and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; the secondary antioxidant includes at least one of tris(2,4-di-tert-butylphenyl)phosphite and bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0033] The antioxidant consists of a primary antioxidant and a secondary antioxidant. The primary antioxidant includes phenolic antioxidants such as N,N'-1,6-hexamethylene-bis-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide). The secondary antioxidant includes phosphite antioxidants such as triphenyl phosphite tris-(2,4-di-tert-butylphenyl). The mechanism of action of the primary antioxidant is to inhibit the initiation and propagation of oxidation reactions by capturing free radicals. In PBT alloy materials, it can effectively scavenge free radicals generated during the processing and long-term use, which helps prevent the oxidative degradation of polymer chains in the alloy material, thereby maintaining the mechanical properties, appearance, and dimensional stability of the material. The mechanism of action of the secondary antioxidant mainly plays an antioxidant role by decomposing hydroperoxides. Hydroperoxides are intermediate products in oxidation reactions and can further initiate free radical chain reactions, accelerating the aging of the material. The secondary antioxidant works synergistically with the primary antioxidant and can play a role at different oxidation stages, forming a complete antioxidant system.

[0034] In some possible embodiments, the lubricant is one or a mixture of two of pentaerythritol stearate and ethylene bisstearamide (EBS).

[0035] As a lubricant, pentaerythritol stearate can reduce the melt viscosity during the processing of alloy materials. In the molten state of PBT alloy materials, pentaerythritol stearate molecules can play a lubricating role between polymer molecular chains, reducing the frictional force between molecular chains. This helps the material flow more easily in processing equipment such as twin-screw extruders, making the processing process smoother. EBS also has good lubricating properties. It can form a lubricating film in the alloy material, further improving the fluidity of the material. Especially in alloy materials filled with fillers such as glass fiber and mineral powder, EBS can reduce the frictional force between the filler and the resin matrix, as well as the agglomeration phenomenon between fillers, making the fillers more evenly distributed in the material, and at the same time also contributing to the overall flow of the material and improving the molding quality.

[0036] In some possible embodiments, the compatibilizer is a terpolymer of styrene-acrylonitrile-glycidyl methacrylate (SAG) or a copolymer of ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA).

[0037] The styrene segments in SAG have good affinity with the styrene phase in ABS / ASA, and the acrylonitrile segments can also interact with the acrylonitrile part in ABS. The epoxy groups of glycidyl methacrylate can undergo chemical reactions with the terminal hydroxyl groups and terminal carboxyl groups of PBT, forming chemical bonding between PBT and ABS / ASA, thereby enhancing the compatibility between the two phases and making the alloy system more stable. The ethylene segments in E-MA-GMA can have good compatibility with the aliphatic segments in PBT. The methacrylic acid groups can interact with the polar groups of PBT. The epoxy groups of glycidyl methacrylate can also react with the end groups of PBT and have a certain affinity with the polar groups in ABS / ASA, effectively reducing the interfacial tension between PBT and ABS / ASA, promoting the uniform dispersion of the phases, and improving the compatibility of the alloy.

[0038] In some possible embodiments, the black additive includes a masterbatch with carbon black or AS as the carrier.

[0039] The masterbatch with AS (acrylonitrile-styrene copolymer) as the carrier can provide uniform black coloring for the PBT / (ABS / ASA) alloy material. The AS carrier has good compatibility with the ABS and ASA components in the alloy. During the mixing process, the masterbatch can be evenly dispersed in the alloy material, ensuring color consistency.

[0040] Based on a general inventive concept, the present application also provides a method for preparing the above-mentioned low-shrinkage PBT alloy material without primer, including the following steps:

[0041] S1: Dry the polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer, and acrylonitrile-styrene-acrylate copolymer in an oven at 80 - 100 °C for 4 - 6 hours to remove moisture;

[0042] S2: Mix the dried polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene-acrylate copolymer, mineral powder, and the weighed primary antioxidant, secondary antioxidant, compatibilizer, lubricant, and black additive evenly in a high-speed mixer to obtain a premix;

[0043] S3: Set the process parameters of the twin-screw extruder. The melting and extrusion temperatures of each section of the twin-screw extruder are: 225 °C - 235 °C for sections 2 - 4, 220 °C - 235 °C for sections 5 - 8, 220 °C - 230 °C for sections 9 - 10, and 220 °C - 230 °C for the die head;

[0044] S4: The premix is added into the screw cavity of the twin-screw extruder from the main feeding port of the above twin-screw extruder, and the glass fiber is added into the screw cavity of the twin-screw extruder from the side feeding port of the twin-screw extruder. Through sufficient mixing, shearing and plasticization in the twin-screw extruder, each component is uniformly dispersed;

[0045] S5: The material extruded by the twin-screw extruder is granulated by a water-cooled strand pelletizer to obtain PBT / (ABS / ASA) alloy material particles.

[0046] The following describes the present application in further detail with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods without specific conditions noted in the following embodiments are generally determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0047] The experimental raw materials are as follows:

[0048] PBT resin: Bluestar low-bleed PBT 1100HQII

[0049] ABS resin: Chi Mei PA-757K (butadiene content is 10%-30%)

[0050] ASA: Jinhesi CS-N131A (acrylonitrile content is 20%-30%)

[0051] Mineral powder: Talc powder, Italian IMIFABI HTPultra5L

[0052] Glass fiber (length 3mm, diameter 10μm): Jushi Group ECS10-03-568H (TX)

[0053] Primary antioxidant: Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, BASF antioxidant 1076

[0054] Co- antioxidant: Bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, American DOVER S9228

[0055] Compatibilizer: Shenyang Ketong KT-2

[0056] Lubricant: Lonza PETS

[0057] AS carrier black masterbatch: Dongguan Ruiyi AS carrier high-gloss black masterbatch A4005

[0058] Example 1

[0059] The bottom-coat-free low-shrinkage PBT alloy material of this embodiment, by weight, comprises the following components: 50.5 parts of polybutylene terephthalate resin, 20 parts of acrylonitrile-butadiene-styrene copolymer, 10 parts of acrylonitrile-styrene-acrylate copolymer, 0.5 part of primary antioxidant, 0.5 part of secondary antioxidant, 0.5 part of compatibilizer, 10 parts of glass fiber, 5 parts of mineral powder, 1.0 part of lubricant, and 2.0 parts of black additive.

[0060] The preparation method of the above bottom-coat-free low-shrinkage PBT alloy material, the preparation flow chart is as Figure 1 shown, and the steps are as follows:

[0061] (1) Symmetrically weigh the polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer, and acrylonitrile-styrene-acrylate copolymer and dry them in an oven at 100 °C for 4 hours to remove moisture;

[0062] (2) Weigh each component according to the weight parts of the raw material components of this embodiment, and mix the dried polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene-acrylate copolymer, mineral powder, and the weighed primary antioxidant, secondary antioxidant, compatibilizer, lubricant, and black additive evenly in a high-speed mixer to obtain a premix;

[0063] (3) Set the process parameters of the twin-screw extruder. The melting and extrusion temperatures of each section of the twin-screw extruder are: 225 °C for sections 2-4, 220 °C for sections 5-8, 220 °C for sections 9-10, and 220 °C for the die head;

[0064] (4) Add the premix described in step (2) from the main feeding port of the twin-screw extruder into the screw cavity of the twin-screw extruder, and add the glass fiber from the side feeding port of the twin-screw extruder into the screw cavity of the twin-screw extruder. After sufficient mixing, shearing, and plasticization in the twin-screw extruder, each component is evenly dispersed;

[0065] (5) The material extruded by the twin-screw extruder is granulated by a water-cooled strand pelletizer to obtain PBT / (ABS / ASA) alloy material pellets.

[0066] Example 2

[0067] The bottom-coat-free low-shrinkage PBT alloy material of this embodiment, by weight, comprises the following components: 44.4 parts of polybutylene terephthalate resin, 17 parts of acrylonitrile-butadiene-styrene copolymer, 13 parts of acrylonitrile-styrene-acrylate copolymer, 0.3 part of primary antioxidant, 0.3 part of secondary antioxidant, 1.5 part of compatibilizer, 12 parts of glass fiber, 8 parts of mineral powder, 2.0 part of lubricant, and 1.5 parts of black additive.

[0068] The preparation method of the above-mentioned primer-free PBT alloy material with low shrinkage rate is as follows:

[0069] (1) Weigh the polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer and acrylonitrile-styrene-acrylate copolymer, and dry them in an oven at 80°C for 6 hours to remove moisture;

[0070] (2) Weigh each component according to the weight parts of the raw material components in this embodiment. Mix the dried polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene-acrylate copolymer, mineral powder, and the weighed primary antioxidant, secondary antioxidant, compatibilizer, lubricant, and black additive evenly in a high-speed mixer to obtain a premix;

[0071] (3) Set the process parameters of the twin-screw extruder. The melting and extrusion temperature of each section of the twin-screw extruder is: 230°C for sections 2-4, 225°C for sections 5-8, 225°C for sections 9-10, and 225°C for the die head;

[0072] (4) Add the premix described in step (2) into the screw cavity of the twin-screw extruder from the main feeding port of the twin-screw extruder, and add glass fiber into the screw cavity of the twin-screw extruder from the side feeding port of the twin-screw extruder. After sufficient mixing, shearing and plasticization in the twin-screw extruder, make each component evenly dispersed;

[0073] (5) Granulate the material extruded by the twin-screw extruder through a water-cooled strand pelletizer to obtain PBT / (ABS / ASA) alloy material particles.

[0074] Example 3

[0075] The primer-free PBT alloy material with low shrinkage in this embodiment, by weight, includes the following components: 38.6 parts of polybutylene terephthalate resin, 15 parts of acrylonitrile-butadiene-styrene copolymer, 15 parts of acrylonitrile-styrene-acrylate copolymer, 0.2 part of primary antioxidant, 0.2 part of secondary antioxidant, 2.0 parts of compatibilizer, 15 parts of glass fiber, 10 parts of mineral powder, 3.0 parts of lubricant, and 1.0 part of black additive.

[0076] The preparation method of the above-mentioned primer-free PBT alloy material with low shrinkage rate is as follows:

[0077] (1) Weigh the polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer and acrylonitrile-styrene-acrylate copolymer, and dry them in an oven at 90°C for 5 hours to remove moisture;

[0078] (2) Weigh each component according to the weight parts of each component of the raw materials in this embodiment. Mix the dried polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene-acrylate copolymer, mineral powder, and the weighed primary antioxidant, secondary antioxidant, compatibilizer, lubricant, and black additive evenly in a high-speed mixer to obtain a premix;

[0079] (3) Set the process parameters of the twin-screw extruder. The temperature of each section of the twin-screw extruder for melting and extrusion is: 235 °C for sections 2-4, 235 °C for sections 5-8, 230 °C for sections 9-10, and 230 °C for the die head;

[0080] (4) Add the premix described in step (2) from the main feeding port of the twin-screw extruder into the screw cavity of the twin-screw extruder, and add glass fiber from the side feeding port of the twin-screw extruder into the screw cavity of the twin-screw extruder. Through sufficient mixing, shearing, and plasticization in the twin-screw extruder, each component is evenly dispersed;

[0081] (5) The material extruded by the twin-screw extruder is granulated by a water-cooled strand pelletizer to obtain PBT / (ABS / ASA) alloy material pellets.

[0082] Comparative Example 1

[0083] The bottom-coat-free low-shrinkage PBT alloy material of this comparative example, by weight, includes the following components: 44.4 parts of polybutylene terephthalate resin, 30 parts of acrylonitrile-butadiene-styrene copolymer, 0.3 part of primary antioxidant, 0.3 part of secondary antioxidant, 1.5 parts of compatibilizer, 12 parts of glass fiber, 8 parts of mineral powder, 2.0 parts of lubricant, and 1.5 parts of black additive.

[0084] The preparation method of the above-mentioned bottom-coat-free low-shrinkage PBT alloy material is to weigh each component according to the weight parts of each component of the raw materials in this comparative example, and the process parameters are the same as those in Example 2.

[0085] Comparative Example 2

[0086] The bottom-coat-free low-shrinkage PBT alloy material of this comparative example, by weight, includes the following components: 44.4 parts of polybutylene terephthalate resin, 17 parts of acrylonitrile-butadiene-styrene copolymer, 13 parts of acrylonitrile-styrene-acrylate copolymer, 0.3 part of primary antioxidant, 0.3 part of secondary antioxidant, 1.5 parts of compatibilizer, 20 parts of glass fiber, 2.0 parts of lubricant, and 1.5 parts of black additive.

[0087] The preparation method of the above-mentioned bottom-coat-free low-shrinkage PBT alloy material is to weigh each component according to the weight parts of each component of the raw materials in this comparative example, and the process parameters are the same as those in Example 2.

[0088] Comparative Example 3

[0089] The bottom-coat-free low-shrinkage PBT alloy material of this comparative example includes the following components by weight: 44.4 parts of polybutylene terephthalate resin, 17 parts of acrylonitrile-butadiene-styrene copolymer, 13 parts of acrylonitrile-styrene-acrylate copolymer, 0.3 part of main antioxidant, 0.3 part of auxiliary antioxidant, 1.5 parts of compatibilizer, 20 parts of mineral powder, 2.0 parts of lubricant, and 1.5 parts of black additive.

[0090] The preparation method of the above-mentioned bottom-coat-free low-shrinkage PBT alloy material is to weigh each component according to the weight parts of each component of the raw materials in this comparative example, and the process parameters are the same as those in Example 2.

[0091] The specific raw material component weight fractions of each example and comparative example are shown in Table 1 as follows:

[0092] Table 1 Raw material component weight parts

[0093] Component Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 PBT resin 50.5 44.4 38.6 44.4 44.4 44.4 ABS 20.0 17.0 15.0 30.0 17.0 17.0 ASA 10.0 13.0 15.0 - 13.0 13.0 Primary antioxidant 0.5 0.3 0.2 0.3 0.3 0.3 Secondary antioxidant 0.5 0.3 0.2 0.3 0.3 0.3 Glass fiber 10.0 12.0 15.0 12.0 20.0 - Mineral powder 5.0 8.0 10.0 8.0 - 20.0 Compatibilizer 0.5 1.5 2.0 1.5 1.5 1.5 Lubricant 1.0 2.0 3.0 2.0 2.0 2.0 Black additive 2.0 1.5 1.0 1.5 1.5 1.5

[0094] The prepared PBT alloy material is made into sample strips for testing. The test results are shown in Table 2 below, and the specific test standards are as follows:

[0095] Tensile property test: The test standard is ISO 527, and the tensile rate is 50 mm / min.

[0096] Flexural property test: The test standard is ISO-178, and the flexural rate is 2 mm / min.

[0097] Izod impact strength: The test standard is ISO-179.

[0098] Mass melt index: The test standard is ISO 1133-1, the test temperature / load: 260 °C / 5 KG, and the die selection: full die.

[0099] Shrinkage rate test: The test standard is ISO 294-4.

[0100] Bottom-coat-free test: The test standard is ISO 2409. The rating results usually range from level 0 to level 5. Level 0 indicates the best adhesion performance with no coating peeling off, and level 5 indicates the worst adhesion performance with large-area coating peeling off.

[0101] Table 2 Test results

[0102]

[0103] As can be seen from Table 2, a kind of primerless low-shrinkage PBT alloy material prepared in the embodiments of the present invention has a lower shrinkage rate compared with the comparative example (the shrinkage rate of primerless PBT is usually 1.5-2.0%), and has good mechanical properties, heat resistance and chemical stability. Mechanical property indexes such as tensile strength, flexural modulus and notched impact strength are excellent, and it can meet the requirements of the fields of electronic appliances, automobiles, machinery, etc. for the strength and toughness of materials.

[0104] In Examples 1-3, by increasing the proportion of glass fiber and mineral powder and decreasing the proportion of ABS:ASA, although the strength is improved, the shrinkage rate performance is slightly decreased. The increase in strength is because glass fiber has high strength and high modulus and bears stress like a skeleton, and mineral powder also has a certain strengthening effect. The increase of both makes the material able to bear greater external force. The failure to reduce the shrinkage rate is because too much glass fiber and mineral powder are unevenly dispersed in the matrix, generating internal stress, and the difference in thermal expansion coefficient between them and the matrix is large, which exacerbates the non-uniformity of shrinkage.

[0105] By comparing Example 2 with Comparative Examples 1 - 3, where the difference between Comparative Example 2 and Comparative Example 3 lies in the fillers. Glass fiber and mineral powder are used as fillers, and their performance effects are different. Adding glass fiber can significantly improve the strength because glass fiber has high strength and high modulus, acting like a framework to bear stress and effectively preventing crack propagation; the strengthening effect of mineral powder is weaker. The shrinkage rate is reduced because glass fiber has a low coefficient of thermal expansion, restricting the shrinkage of the matrix during cooling, and its network structure also hinders the movement of molecular chains; although mineral powder can also reduce the shrinkage rate, its effect is not as good as that of glass fiber. However, glass fiber increases the melt flow resistance. Its large aspect ratio and strong interaction with the matrix result in a decrease in the melt index, while mineral powder has less impact. In terms of the primerless performance, the surface of glass fiber is smooth and has low chemical activity, with poor adhesion to the coating; the surface of mineral powder has active groups and large roughness, which is beneficial for binding with the coating and performs better in primerless applications. Therefore, the fillers were adjusted to mineral powder and glass fiber. Example 2 is based on Comparative Example 2 and Comparative Example 3, adding glass fiber and mineral powder and optimizing their proportions. The use of a mixed filler of glass fiber and mineral powder has a significant effect. Glass fiber has a low coefficient of thermal expansion, which can restrict the shrinkage of the matrix during cooling, and its network structure can also hinder the movement of molecular chains. Mineral powder also has a certain effect on reducing the shrinkage rate. The combination of the two synergistically optimizes the shrinkage performance; the active groups on the surface of mineral powder react with the coating chemically, and the large roughness increases mechanical interlocking, making up for the disadvantage of glass fiber being unfavorable for primerless applications and improving the primerless performance; glass fiber effectively bears and transfers stress to increase the strength. Although the strengthening effect of mineral powder is limited, it does not affect the overall strength to meet the standard; glass fiber increases the melt flow resistance, and mineral powder has little impact on the flow performance. The combination of the two makes the melt index qualified, achieving good effects of significantly improved low shrinkage and primerless performance, with both strength and melt index meeting the standards. The difference between Comparative Example 1 and Example 2 is the absence of ASA. Adding ASA significantly improves the performance; in terms of strength, the acrylate rubber phase in ASA can effectively disperse stress, prevent crack propagation, and synergistically act with PBT and ABS to enhance the intermolecular force, making the material more capable of withstanding external forces; in terms of shrinkage rate, ASA has a relatively stable molecular structure and a low coefficient of thermal expansion. During the cooling process, it restricts each other with PBT and ABS, reducing the shrinkage space of molecular chains and lowering the overall shrinkage rate; in terms of primerless performance, the surface of ASA is rich in polar groups, has a strong affinity with the active components in the coating, can form strong chemical bonds and physical adsorption, improving the binding ability between the material surface and the coating, enhancing the primerless effect, and making the comprehensive performance of the material better.

[0106] In summary, the PBT alloy material prepared according to the formula ratio of the present application has a low shrinkage rate, has good affinity with coatings, inks, etc., can achieve firm adhesion without primer coating operation, simplifies the production process, reduces costs, and reduces environmental pollution. The preparation method has a simple process and controllable parameters, and can be efficiently produced using common high-speed stirring and twin-screw extrusion equipment, which is easy to realize industrial-scale manufacturing and has good market promotion prospects.

[0107] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A primerless PBT alloy material with low shrinkage rate, characterized in that, The raw material composition is calculated by weight and includes the following components: 38.6-50.5 parts of polybutylene terephthalate resin, 15-20 parts of acrylonitrile-butadiene-styrene copolymer, 10-15 parts of acrylonitrile-styrene-acrylate copolymer, 0.2-0.5 parts of primary antioxidant, 0.2-0.5 parts of auxiliary antioxidant, 0.5-2.0 parts of compatibilizer, 10-15 parts of glass fiber, 5-10 parts of mineral powder, 1.0-3.0 parts of lubricant and 1.0-2.0 parts of black additive.

2. The low shrinkage PBT alloy material without primer according to claim 1, characterized in that, The polybutylene terephthalate resin has an intrinsic viscosity of 0.8-1.2 dL / g.

3. The low shrinkage PBT alloy material without primer according to claim 2, wherein The content of butadiene in the acrylonitrile-butadiene-styrene copolymer is 10-30%, and the content of acrylonitrile in the acrylonitrile-styrene-acrylate copolymer is 20-30%.

4. The primerless low shrinkage PBT alloy material according to claim 3, characterized in that, The mineral powder is at least one of talcum powder, mica powder and kaolin, and the glass fiber is an alkali-free chopped glass fiber with a length of 3-6 mm and a diameter of 10-15 μm and treated with a silane coupling agent.

5. The low shrinkage PBT alloy material without primer according to claim 4, characterized in that The primary antioxidant comprises at least one of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl alcohol ester; the secondary antioxidant is at least one of tris(2,4-di-tert-butylphenyl)phosphite and bis(2,4-dicumylphenyl)pentaerythritol di(phosphite) ester.

6. The primerless low shrinkage PBT alloy material according to claim 5, characterized in that, The compatibilizer is a terpolymer of styrene-acrylonitrile-glycidyl methacrylate or a copolymer of ethylene-methyl acrylate-glycidyl methacrylate.

7. The primerless low shrinkage PBT alloy material according to claim 6, characterized in that, The lubricant is one of pentaerythritol stearate and ethylene bisstearamide or a mixture of the two.

8. The primerless low shrinkage PBT alloy material according to claim 7, characterized in that, The black additive is at least one of an AS carrier black masterbatch and a carbon black masterbatch.

9. The preparation method of the primerless low shrinkage PBT alloy material according to claim 1, characterized in that, Here are the steps: (1) drying polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer and acrylonitrile-styrene-acrylate copolymer at 80-100° C. for 4-6 hours; (2) uniformly mixing the dried polybutylene terephthalate resin, acrylonitrile-butadiene-styrene copolymer and acrylonitrile-styrene-acrylate copolymer, primary antioxidant, secondary antioxidant, compatibilizer, mineral powder, lubricant and black additive according to weight proportions to obtain a premix; (3) The premix obtained in step (2) and glass fiber are melt-extruded, pelletized, and sieved to obtain a primer-free, low-shrinkage PBT alloy material.

10. The preparation method of the primer-free PBT alloy material with low shrinkage rate according to claim 9, characterized in that, The temperature of each section of the melt extrusion is: 225-235°C for sections 2-4, 220-235°C for sections 5-8, 220-230°C for sections 9-10, and 220-230°C for the die.

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