CN113652062B - PBT/PC alloy with stable mechanical property, preparation method and product thereof - Google Patents

Abstract

The invention discloses a PBT/PC alloy with stable mechanical properties and a preparation method thereof. The PBT/PC alloy comprises the following components in parts by weight: 50-80 parts of a PBT/PC mixture, 10-40 parts of glass fiber, 2-5 parts of epoxy resin, 0.1-0.3 part of an antioxidant, 4-8 parts of a toughening agent and 2-4 parts of trimethyl allyl isocyanate; the weight ratio of PBT to PC in the PBT/PC mixture is (2-6) to 1, and the toughening agent is an organosilicon-acrylate core-shell structure toughening agent. According to the invention, the mechanical property retention rate of the PBT/PC alloy after multiple injection molding is effectively improved through the synergistic effect of the tri-allyl isocyanate, the toughening agent with the core-shell structure and the epoxy resin. The mechanical property retention rate of the PBT/PC alloy subjected to secondary injection molding is not less than 95%, the mechanical property retention rate of the PBT/PC alloy subjected to tertiary injection molding is not less than 90%, and the PBT/PC alloy can resist repeated cycle injection molding.

Description

PBT/PC alloy with stable mechanical property, preparation method and product thereof

Technical Field

The invention relates to the technical field of engineering plastics, in particular to a PBT/PC alloy with stable mechanical property, a preparation method thereof and a product.

Background

Polycarbonate (PC) is a noncrystalline thermoplastic with high impact strength and excellent creep resistance, and polybutylene terephthalate (PBT) is a crystalline thermoplastic with the advantages of high crystallization speed, high rigidity, excellent chemical resistance, good melt fluidity and the like. The blending modification of the PC and the PBT can not only make up the defects of high melt viscosity, poor fluidity, poor solvent resistance and the like of the PC, but also improve the defects of low impact resistance and the like of the PBT, and can be widely applied to the fields of automobile engineering, electronic and electrical engineering, sports and leisure articles.

However, the chain end of the PC molecule has-OH group, the chain end of the PBT molecule has-OH and-COOH group, and the PC and the PBT are easy to generate side reactions such as ester exchange reaction, alcoholysis acidolysis and the like during melt blending, so that the mechanical property of the PBT/PC alloy is unstable.

Meanwhile, the PBT/PC alloy generally generates a large amount of casting system solidified materials without using value, namely, nozzle materials in the injection molding process. Generally, when a PBT/PC alloy nozzle material is ground and then injection molded twice, the performance of the material is greatly deteriorated, and thus the material cannot be recycled for many times, which results in huge waste.

In general, after the PBT/PC alloy is used by secondary injection molding, the retention rate of the mechanical property of the PBT/PC alloy is below 75% of the property of a new material; after the three-time injection molding is used, the mechanical property retention rate is further reduced to below 50%, and the application requirements of products can not be met in most occasions. In the prior art, in order to avoid resource waste, the water gap material of the PBT/PC alloy is recycled, and the water gap material is usually blended into a new material in a certain proportion by a new material and old material blending mode. However, in this method, the nozzle material cannot be used directly, and the recycling efficiency is poor.

Therefore, a PBT/PC alloy with stable mechanical properties needs to be developed, the PBT/PC alloy nozzle material does not need to be blended with a new material, and the PBT/PC alloy nozzle material is directly subjected to cycle injection molding and still maintains good mechanical properties.

Disclosure of Invention

The PBT/PC alloy has stable mechanical property, the mechanical property retention rate of the PBT/PC alloy after secondary injection molding is more than or equal to 95%, and the mechanical property retention rate of the PBT/PC alloy after tertiary injection molding is more than or equal to 90%.

The invention also aims to provide a preparation method of the PBT/PC alloy with stable mechanical properties.

Another object of the invention is to provide a PBT/PC alloy product, which is made of the PBT/PC alloy nozzle material.

In order to solve the technical problems, the invention adopts the technical scheme that:

the PBT/PC alloy with stable mechanical properties comprises the following components in parts by weight:

50-80 parts of a PBT/PC mixture,

10-40 parts of glass fiber,

2-5 parts of epoxy resin,

0.1 to 0.3 part of antioxidant,

4-8 parts of a toughening agent,

2-4 parts of trimethyl allyl isocyanate (TMAIC);

the weight ratio of PBT to PC in the PBT/PC mixture is (2-6) to 1,

the toughening agent is an organosilicon-acrylate core-shell structure toughening agent.

The inventor researches and discovers that because molecular structures of PBT and PC contain ester groups, in the process of multiple times of injection molding, due to higher injection molding temperature and larger shearing force, ester exchange reaction is easy to occur between PBT and PC, so that the crystallization capability of a PBT/PC system is greatly reduced, and the mechanical property of the PBT/PC alloy material is reduced.

Trimethallyl isocyanate (TMAIC) of formula C ₁₅ H ₂₁ N ₃ O ₃ Is a polymer crosslinking aid suitable for use at higher processing temperatures. During the injection molding process of the PBT/PC alloy, TMAIC can rapidly initiate a cross-linking reaction between molecular chains in a PBT/PC system, and make up for the reduction of the mechanical properties of the alloy caused by ester exchange between PBT molecules and PC molecules to the maximum extent, thereby greatly improving the property retention rate of the alloy material during multiple injection molding processes.

The inventors have found that other types of crosslinking aids for polymeric materials, such as organic peroxides and acrylate-based crosslinking agents, do not provide excellent crosslinking promotion comparable to that of TMAIC in PBT/PC systems.

The toughening agent is an organosilicon-acrylate core-shell structure toughening agent, the shell part provides good dispersibility and compatibility with matrix resin, and the core part can absorb and disperse impact energy. Compared with a toughening agent with a non-core-shell structure, the toughening agent with the core-shell structure has more excellent toughening effect in the PBT/PC alloy system.

Through the synergistic effect of the toughening agent and the TMAIC, on one hand, the initial mechanical property of the PBT/PC alloy is improved, on the other hand, the performance reduction of the alloy in multiple injection molding processes is reduced, and good performance retention rate is obtained.

Preferably, the acid value of TMAIC is less than or equal to 1 mgKOH/g.

The acid value test method is in accordance with GB/T264-1983.

When the acid value of TMAIC is too high, the PBT/PC system is unstable, the initiation promotion effect on the cross-linking reaction between PBT and PC molecular chains is slow, and the mechanical property retention rate of the PBT/PC alloy is influenced.

Preferably, the toughening agent is a shell of methyl methacrylate or grafted polymethyl methacrylate and a core of a crosslinked acrylate-silicone copolymer.

Alternatively, the toughening agent may be S-2501, S-2001, S-2006, Mitsubishi Yang corporation, Brillouin MR-502, DONGEM S-203, or BSMCMX-520S/550S.

Preferably, the PC is one or more of aromatic polycarbonate, aliphatic polycarbonate, aromatic-aliphatic polycarbonate, branched polycarbonate or siloxane copolycarbonate.

More preferably, the PC is an aromatic polycarbonate.

Preferably, the aromatic polycarbonate has a viscosity average molecular weight of 13000 to 40000.

More preferably, the aromatic polycarbonate has a viscosity average molecular weight of 18000 to 28000.

The method for detecting the viscosity-average molecular weight of the PC comprises the following steps: the solvent is dichloromethane, and the solvent is obtained by calculation of the Ubbelohde viscosity at the test temperature of 25 ℃.

The inventors have found that PC having a viscosity-average molecular weight in the above range can provide an alloy with more excellent mechanical strength retention as a matrix resin of a PBT/PC alloy.

Preferably, the PBT has an intrinsic viscosity of 0.7-1.1 dL/g at 25 ℃.

The intrinsic viscosity test method of PBT is in accordance with GB/T14190-2017.

The inventors have found that this viscosity range of PBT enables the PBT/PC alloy of the invention to have higher retention of the two-shot moldability.

Preferably, the glass fibers are treated with a coupling agent.

More preferably, the coupling agent is a blend of N- (β -aminoethyl) - γ -aminopropyltrimethoxysilane, γ -methacryloxypropyltrimethoxysilane, isopropyldi (methacryloyl) isostearoyl titanate.

Further preferably, the blending weight ratio of the N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane, the gamma-methacryloxypropyltrimethoxysilane and the isopropyl bis (methacryloyl) isostearoyl titanate is 2:1: 3.

The glass fiber treated by the coupling agent has more excellent interface performance with PBT and PC components. And during the process of secondary injection molding or tertiary injection molding, better performance retention rate can be maintained.

The inventor researches and discovers that the higher proportion of the isopropyl di (methacryloyl) isostearyl titanate coupling agent can endow the PC resin with more excellent interfacial bonding force with the glass fiber, and the preferable proportion of 2:1:3 can ensure that the glass fiber has the best interfacial bonding force with the PBT resin and the PC resin.

Preferably, the epoxy resin is bisphenol A type glycidyl ether, and the epoxy equivalent is less than 600 g/eq.

More preferably, the epoxy equivalent of the epoxy resin is 450 to 500 g/eq.

The test method of the epoxy equivalent is in accordance with GB/T4612-2008.

Under the combined action of the epoxy resin, the flexibilizer and the TMAIC, the mechanical property retention rate of the PBT/PC alloy can be kept at a good level in the process of multiple times of cycle injection molding. A large amount of creative experimental data show that when one component or two components are lacked, the PBT/PC alloy can not achieve the mechanical property maintaining effect.

Preferably, the antioxidant is a hindered phenol antioxidant.

Optionally, the antioxidant is beta (3, 5 di-tert-butyl-4-hydroxyphenyl) octadecyl propionate (antioxidant 1076) and/or 1,3, 5-tris (4-tert-butyl-3-hydroxy-2, 6-dimethylbenzyl) -1,3, 5-triazine-2, 4,6- (1H,3H,5H) -trione.

The invention also provides a preparation method of the PBT/PC alloy, which comprises the following steps:

mixing epoxy resin, an antioxidant, a toughening agent and TMAIC to obtain a premix;

and mixing the PBT, the PC, the glass fiber and the premix, adding the mixture into an extruder, and performing melt extrusion granulation to obtain the PBT/PC alloy.

Preferably, the extruder is a twin screw extruder.

More preferably, the temperature of the twin-screw extruder from the feeding port to the head in the first zone is 200-230 ℃, the temperature of the twin-screw extruder in the second zone is 240-260 ℃, the temperature of the third zone is 235-255 ℃, the temperature of the fourth zone is 235-255 ℃, the temperature of the fifth zone is 235-255 ℃, the temperature of the sixth zone is 240-260 ℃, the temperature of the seventh zone is 240-260 ℃, the temperature of the eighth zone is 220-240 ℃, the temperature of the ninth zone is 220-240 ℃, the temperature of the tenth zone is 240-260 ℃, and the screw rotating speed of the twin-screw extruder is 200-450 revolutions per minute.

The invention also protects a PBT/PC alloy product which is directly processed by the water gap material of the PBT/PC alloy.

The processing method of the PBT/PC alloy product can be as follows:

and adding the PBT/PC alloy water gap material into an injection molding machine, and performing injection molding at 220-270 ℃.

Compared with the prior art, the invention has the beneficial effects that:

according to the invention, through the synergistic effect of the tri-substituted allyl isocyanate, the organic silicon-acrylate flexibilizer with the core-shell structure and the epoxy resin, the mechanical property retention rate of the PBT/PC alloy after multiple injection molding is effectively improved, and the mechanical property stability of the PBT/PC alloy is improved. The TMAIC can rapidly initiate cross-linking reaction between molecular chains, effectively prevents the molecular chains of PBT and PC from breaking, thereby reducing the degradation of PBT/PC alloy in the process of multiple injection molding; meanwhile, due to the synergistic effect of the toughening agent and the epoxy resin, the mechanical property retention rate of the PBT/PC alloy is further improved. The mechanical property retention rate of the PBT/PC alloy subjected to secondary injection molding is not less than 95%, and the mechanical property retention rate of the PBT/PC alloy subjected to tertiary injection molding is not less than 90%, so that the PBT/PC alloy is suitable for being used in multiple times of cyclic injection molding.

Detailed Description

The present invention will be further described with reference to the following embodiments.

The raw materials in the examples and comparative examples are all commercially available;

reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Examples 1 to 19

The PBT/PC alloys of examples 1 to 19 had the contents of the respective components shown in Table 1.

The preparation method comprises the following steps: blending coupling agents N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane and isopropyl di (methacryloyl) isostearyl titanate according to the weight ratio of 2:1:3, and then coupling the glass fiber to obtain the coupled glass fiber;

mixing the epoxy resin, the antioxidant, the toughening agent and TMAIC according to table 1 to obtain a premix; and mixing the PBT, the PC, the glass fiber subjected to coupling treatment or the glass fiber not subjected to coupling treatment and the premix, adding the mixture into a double-screw extruder, and performing melt extrusion granulation to obtain the PBT/PC alloy.

The temperature of a first zone from a feeding port to a machine head of the double-screw extruder is 200-230 ℃, the temperature of a second zone is 240-260 ℃, the temperature of a third zone is 235-255 ℃, the temperature of a fourth zone is 235-255 ℃, the temperature of a fifth zone is 235-255 ℃, the temperature of a sixth zone is 240-260 ℃, the temperature of a seventh zone is 240-260 ℃, the temperature of an eighth zone is 220-240 ℃, the temperature of a ninth zone is 220-240 ℃, the temperature of a tenth zone is 240-260 ℃, and the screw rotating speed of the double-screw extruder is 200-450 revolutions per minute.

TABLE 1 PBT/PC alloys of examples 1 to 19 having the contents of the respective components (parts by weight)

Comparative examples 1 to 6

The PBT/PC alloy of comparative examples 1 to 6 has the contents of the respective components shown in Table 2.

The preparation method comprises the following steps: mixing epoxy resin, antioxidant, toughener and TMAIC (if any) according to table 2 to obtain a premix; and mixing the PBT, the PC, the glass fiber and the premix, adding the mixture into a double-screw extruder, and performing melt extrusion granulation to obtain the PBT/PC alloy.

The temperature of the double-screw extruder from a feeding port to a nose in a first zone is 200-230 ℃, the temperature of a second zone is 240-260 ℃, the temperature of a third zone is 235-255 ℃, the temperature of a fourth zone is 235-255 ℃, the temperature of a fifth zone is 235-255 ℃, the temperature of a sixth zone is 240-260 ℃, the temperature of a seventh zone is 240-260 ℃, the temperature of an eighth zone is 220-240 ℃, the temperature of a ninth zone is 220-240 ℃, the temperature of a tenth zone is 240-260 ℃, and the screw rotating speed of the double-screw extruder is 200-450 revolutions per minute.

TABLE 2 PBT/PC alloys of comparative examples 1 to 6 with respect to the content of each component (parts by weight)

Performance testing

The PBT/PC alloy prepared in the above examples and comparative examples was subjected to the following performance test.

The PBT/PC alloy is subjected to primary injection molding, secondary injection molding and tertiary injection molding, and the specific method comprises the following steps:

primary injection molding: drying the extruded and granulated PBT/PC alloy granules in a 120 ℃ forced air drying oven for 6h, and then performing injection molding through an injection molding machine to obtain an ISO standard mechanical sample strip, namely a primary injection molding mechanical sample strip;

secondary injection molding: crushing the mechanical sample strip obtained by primary injection molding by using a crusher, drying the crushed particles in a 120 ℃ blast drying oven for 6 hours, and then performing injection molding by using an injection molding machine to obtain an ISO standard mechanical sample strip, namely a secondary injection molding mechanical sample strip;

and (3) injection molding for three times: and (3) crushing the mechanical sample strip obtained by secondary injection molding by using a crusher, drying the crushed particles in a 120 ℃ forced air drying oven for 6 hours, and then performing injection molding by using an injection molding machine to obtain an ISO standard mechanical sample strip, namely the three-time injection molding mechanical sample strip.

Mechanical property testing is carried out on the primary/secondary/tertiary injection molding mechanical sample strips respectively, and the specific method for the mechanical property testing comprises the following steps:

tensile strength: measured according to the ISO527-2012 standard method and has the unit of MPa;

notched impact strength: measured according to ISO180-2000 standard method, with kJ/m ² ；

Retention ratio: (test value of secondary injection or tertiary injection/corresponding test value of primary injection) × 100%.

Test results

The results of the performance tests of examples 1 to 19 are shown in Table 3, and the results of the performance tests of comparative examples 1 to 6 are shown in Table 4.

TABLE 3 results of Performance test of examples 1 to 19

From the test results in Table 1, the mechanical property retention rate of the PBT/PC alloy of the embodiments 1 to 19 after the secondary injection is not less than 95% compared with the primary injection, and the mechanical property retention rate of the PBT/PC alloy after the third injection is not less than 90% compared with the primary injection. This shows that the PBT/PC alloy of the invention has little loss of mechanical properties after multiple cycles of injection molding, and still maintains higher rigidity and toughness.

From examples 1 to 5, the PC is preferably an aromatic polycarbonate, more preferably an aromatic polycarbonate having a viscosity average molecular weight of 18000 to 28000. Within the range, the PBT/PC alloy has better mechanical property retention rate after secondary injection molding or tertiary injection molding. In examples 1 and 7 to 8, the weight ratio of PBT to PC is preferably (2 to 4): 1. According to the test results of the embodiment 1 and the embodiment 10, when the acid value of TMAIC is less than or equal to 1mg KOH/g, the mechanical property retention rate of the PBT/PC alloy is higher. From examples 1 and 15, the toughening agent preferably has grafted polymethylmethacrylate as the shell and a crosslinked acrylate-silicone copolymer as the core.

From example 13, the mechanical property retention rate of the PBT/PC alloy prepared by the coupling agent-untreated glass fiber after multiple cycles of injection molding is slightly poor.

TABLE 4 Performance test results for comparative examples 1-6

According to the test results in table 4, in comparative examples 1 to 3, when the epoxy resin, the toughening agent or the TMAIC lacks a certain component, the PBT/PC alloy cannot obtain a high mechanical property retention rate, which indicates that the epoxy resin, the toughening agent and the TMAIC must be used in combination to achieve a synergistic effect.

Compared with the prior art, the toughening agent in the comparative example 4 is not a core-shell structure, the cross-linking agent 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane is used for replacing TMAIC in the comparative example 5, and the mechanical property retention rate of the prepared PBT/PC alloy after secondary injection molding is less than or equal to 88 percent, and the mechanical property retention rate after tertiary injection molding is less than or equal to 81 percent. The mechanical retention rates of comparative example 4 and comparative example 5 are improved to a certain extent compared with comparative examples 1 to 3, but the mechanical retention rates are not as excellent as those of the examples of the invention.

In comparative example 6, the weight ratio of PBT to PC is 1: 1, which is beyond the range of the weight ratio of PBT to PC in the technical scheme of the invention, and the prepared PBT/PC alloy is difficult to maintain excellent mechanical properties after secondary and tertiary injection molding.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (5)

1. The PBT/PC alloy with stable mechanical properties is characterized by comprising the following components in parts by weight:

50-80 parts of a PBT/PC mixture, 10-40 parts of glass fiber, 2-5 parts of epoxy resin, 0.1-0.3 part of an antioxidant, 4-8 parts of a toughening agent and 2-4 parts of trimethyl allyl isocyanate;

the acid value of the trimethyl allyl isocyanate is less than or equal to 1 mgKOH/g;

the weight ratio of PBT to PC in the PBT/PC mixture is (2-6) to 1,

the toughening agent takes methyl methacrylate or grafted polymethyl methacrylate as a shell and takes cross-linked acrylate-organosilicon copolymer as a core;

the PC is an aromatic polycarbonate, and the viscosity average molecular weight of the aromatic polycarbonate is 13000-40000.

2. The PBT/PC alloy of claim 1, wherein the PBT has an intrinsic viscosity of 0.7 to 1.1dL/g at 25 ℃.

3. The PBT/PC alloy of claim 2, wherein the epoxy resin is a bisphenol A glycidyl ether with an epoxy equivalent of < 600 g/eq.

4. The preparation method of the PBT/PC alloy according to any one of claims 1 to 3, characterized by comprising the following steps:

mixing epoxy resin, an antioxidant, a toughening agent and trimethallyl allyl isocyanate to obtain a premix;

and mixing the PBT, the PC, the glass fiber and the premix, adding the mixture into an extruder, and performing melt extrusion granulation to obtain the PBT/PC alloy.

5. A PBT/PC alloy product is characterized by being directly processed from the water gap material of the PBT/PC alloy of any one of claims 1 to 3.