Preparation method of radiation-resistant PVC (polyvinyl chloride) resin

Abstract

The invention discloses a preparation method of radiation-resistant PVC (polyvinyl chloride) resin, and belongs to the technical field of graft polymer compositions. An existing PVC resin irradiation-resistant modification method is low in irradiation-resistant modification effect or can cause serious influence on the mechanical property of PVC resin, and the method comprises the following steps: 1) uniformly dispersing an initiator, a dispersing agent, an irradiation-resistant agent and a chain transfer agent in water; 2) vacuumizing, adding a vinyl chloride monomer, uniformly stirring at normal temperature, and heating for reaction; (3) adding a terminator, uniformly stirring, and drying to obtain PVC resin; wherein the radiation-resistant agent in the step (1) is a solution prepared from p-methoxycinnamyl oxypropyl trimethoxy silane and 4-methyl-acrylate-2-hydroxybenzophenone according to any proportion. The preparation method comprises the following steps: preparing the radiation-resistant agent from the p-methoxycinnamyl oxypropyl trimethoxy silane and the 4-methyl-acrylate-2-hydroxybenzophenone according to any proportion; and the radiation-resistant component is combined into the PVC resin particles, so that the radiation-resistant capability of the particles is improved essentially. The selected specific radiation-resistant agent component can be well combined with the PVC resin, and the mechanical property of the PVC resin is not influenced or even improved.

Description

Technical Field

[0001] The invention discloses a method for preparing a radiation-resistant PVC resin, belonging to the technical field of grafted polymer compositions. Background Art

[0002] The traditional ethylene oxide sterilization method for medical devices has the disadvantage of ethylene oxide residue, which will have adverse effects on human health and the atmospheric environment. High-energy ray irradiation disinfection has the advantages of high efficiency, safety, and no chemical residue, but PVC resin will produce significant yellowing and decreased mechanical properties after irradiation, which cannot meet the use requirements. Therefore, it is particularly important to develop new radiation-resistant PVC materials.

[0003] Invention patent CN103435725B discloses a water-emulsion type polyvinyl chloride resin terminator. The method firstly dissolves the stabilizer and phenolic antioxidant by stirring, keeps the temperature and cools down to room temperature, then adds the light stabilizer and polymerization inhibitor, stirs evenly, and obtains a mixed terminator solution; then adds the emulsifier to the mixed terminator solution, heats and stirs evenly, mixes the emulsion, and simultaneously mixes the dispersant and water, stirs and heats to obtain a dispersed solution; finally, the dispersed solution is added to the mixed emulsion to obtain a water-emulsion type polyvinyl chloride resin terminator. The invention mixes the light stabilizer with the polymerization inhibitor, that is, the method of using the light stabilizer is to mix it with the polymerization inhibitor into the formed PVC resin chains after the polymerization of the PVC resin is completed. Since the light stabilizer and the PVC resin have different properties and poor compatibility, it is very easy to reduce the mechanical properties of the final PVC resin product.

[0004] Invention patent CN102051006B discloses a radiation-resistant high-resilience polyvinyl chloride composition and a preparation method thereof, wherein polyvinyl chloride resin, plasticizer and powdered nitrile rubber are blended and processed, and after being evenly mixed, the radiation-resistant high-resilience polyvinyl chloride composition is obtained by melt blending. The organic plasticizer and powdered nitrile component used in the patent provide limited improvement in radiation resistance.

[0005] Invention patent CN114685925A discloses a radiation-resistant rigid PVC material and its preparation method and application, using a processing formula composed of grafted modified PVC powder and multiple stabilizers. The stabilizers are organic tin stabilizers and epoxy soybean oil auxiliary stabilizers, but according to the common knowledge of those skilled in the art, organic tin stabilizers are difficult to be well grafted into the long chain of PVC resin, so they will also affect the mechanical properties of the resin; and its principle is to improve the thermal stability of PVC resin and reduce the yellowing of the resin and the decline in mechanical properties, but it cannot well alleviate the yellowing problem caused by radiation. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing a radiation-resistant PVC resin which can improve the radiation resistance of the PVC resin while avoiding reducing the mechanical properties.

[0007] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a radiation-resistant PVC resin, characterized in that it comprises the following steps: 1) Disperse the initiator, dispersant, radiation resistant agent and chain transfer agent evenly in water; 2) Evacuate to -0.9~-0.5MPa, add vinyl chloride monomer, stir evenly at room temperature, raise the temperature to 55~65℃, and react until the pressure reaches 0.2~0.3MPa; 3) Add the terminator, stir evenly, and dry to obtain PVC resin; Wherein, the radiation-resistant agent in step 1) is a solution of p-methoxycinnamoyloxypropyltrimethoxysilane and 4-methyl-acrylate-2-hydroxybenzophenone in any proportion.

[0008] In the process of polymerizing vinyl chloride monomer and forming a macroscopic layer (above 10 μm), the present invention combines the radiation-resistant component into the interior of the PVC resin particles, thereby improving the radiation resistance of the PVC resin from the particle nature. The selected specific radiation-resistant agent component can be well combined with the PVC resin and connected to the PVC resin molecular chain at a microscopic level, thereby improving the radiation resistance of the PVC while not affecting or even improving its mechanical properties.

[0009] Preferably, the weight ratio of p-methoxycinnamoyloxypropyltrimethoxysilane to 4-methyl-acrylate-2-hydroxybenzophenone in the radiation-resistant agent is 1:1-2.

[0010] Preferably, the preparation method of the radiation-resistant agent is: p-methoxycinnamoyloxypropyl trimethoxysilane and 4-methyl-acrylate-2-hydroxybenzophenone are mixed and dissolved in ethyl acetate in a weight ratio of 1:1-2 to obtain a preliminary dispersion, sorbitan monooleate and sodium dodecylbenzenesulfonate are added, and stirred evenly to obtain the radiation-resistant agent. Further preferably, the total weight ratio of p-methoxycinnamoyloxypropyl trimethoxysilane and 4-methyl-acrylate-2-hydroxybenzophenone to the total weight of ethyl acetate is 1:10.

[0011] Using a specific method to disperse the two radiation-resistant agent components can effectively promote the combination of the radiation-resistant agent components and the PVC resin, achieve the addition of radiation-resistant components from the macro and micro levels, improve the radiation resistance effect while further reducing the impact on mechanical properties.

[0012] Further preferably, the weight ratio of the preliminary dispersion to sorbitan monooleate and sodium dodecylbenzene sulfonate is 1:1-5:1-5.

[0013] Further preferably, the uniform stirring is performed by stirring with a high-speed sand mill at a rotation speed of 5000-6000 rpm.

[0014] Preferably, the usage of each raw material is as follows by weight: 100 parts of vinyl chloride monomer, 100-300 parts of deionized water, 0.005-0.2 parts of initiator, 0.005-0.2 parts of dispersant, 0.001-0.3 parts of radiation resistant agent and 0.01-0.05 parts of chain transfer agent.

[0015] More preferably, the method further comprises 0.001 to 0.3 parts of a terminator.

[0016] Preferably, the initiator is a mixture of tert-amyl peroxypivalate (TAPP) and tert-butyl peroxyneodecanoate (TBPND) in a weight ratio of 1:1-2; or a mixture of di(2-ethylhexyl) peroxydicarbonate (EHP) and isopropyl peroxyneodecanoate (ACPND) in a weight ratio of 1:1-2.

[0017] More preferably, the chain transfer agent is diethylhydroxylamine. The terminator is a single terminator of acetone thiosemicarbazone or diethylhydroxylamine; or the terminator is a composite heat-resistant terminator composed of dilauryl thiodipropionate and a hindered phenol antioxidant.

[0018] Preferably, the dispersant is a mixture of hydroxypropyl methylcellulose E50, polyethanol PVA80 and polyethanol PVA55 in a weight ratio of 1:0.2~1:0.1~0.5.

[0019] Preferably, the drying is performed at 50-100° C. in vacuum for 2-6 hours.

[0020] Compared with the prior art, the present invention has the following beneficial effects: the granulation of suspended PVC resin includes macroscopic granulation and submicroscopic and microscopic granulation, and the resin powder structure morphology formed thereby also includes: macroscopic level (above 10µm) particles formed by the aggregation of VCM monomer droplets or particles, microscopic level (below 0.1µm) and submicroscopic level (0.1-10µm) particles formed inside the VCM monomer. The two-level structural morphology determines the final particle characteristics of the PVC resin powder, and has a huge impact on the quality, plasticizing processing performance and product performance of PVC products, which are closely related to the formula and process of PVC suspension polymerization. The radiation-resistant agent in the present invention is combined with the inside of the PVC resin particles when the VCM monomer droplets or particles are aggregated to form particles, thereby improving the radiation resistance of the particles from the essence, while not affecting or even improving the mechanical properties. The p-methoxycinnamoyloxypropyltrimethoxysilane and 4-methyl-acrylate-2-hydroxybenzophenone in the radiation-resistant agent can use their own molecular structure to convert light energy into heat energy, preventing the material from directly absorbing light energy and undergoing photooxidation reactions, thereby improving the light stability of PVC resin and delaying the yellowing and mechanical property degradation of PVC resin when exposed to radiation. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the embodiments, and Embodiment 1 is the best embodiment of the present invention.

[0022] Example 1 A method for preparing a radiation-resistant PVC resin comprises the following steps: 1) Dissolve 0.005 kg of p-methoxycinnamoyloxypropyltrimethoxysilane and 0.005 kg of 4-methyl-acrylate-2-hydroxybenzophenone in 0.05 kg of ethyl acetate, stir to obtain a preliminary dispersion, then mix the preliminary dispersion with 0.05 kg of sorbitan monooleate and 0.05 kg of sodium dodecylbenzenesulfonate, stir in a high-speed sand mill at a speed of 5500 rpm until uniform and without stratification, to obtain a radiation-resistant agent.

[0023] 2) Add 140 kg of deionized water, 0.02 kg of initiator ACPND, 0.03 kg of initiator EHP, 0.02 kg of dispersant E50, 0.01 kg of dispersant PVA80, 0.006 of dispersant PVA55, 0.02 kg of radiation-resistant agent and 0.02 kg of chain transfer agent diethylhydroxylamine into the reactor.

[0024] 3) The reactor was evacuated to -0.09 MPa, 100 kg of vinyl chloride monomer was added, stirred at 470 rpm for 8 min, the temperature was raised to 60.5 °C, and the reaction was continued until the pressure reached 0.3 MPa.

[0025] 4) Add 0.03 kg of acetone thiosemicarbazone as the terminator, stir for 5 min, dehydrate at 3000 rpm, and vacuum dry at 75°C and -0.1 MPa for 6 h to obtain radiation-resistant PVC resin.

[0026] Example 2 A method for preparing a radiation-resistant PVC resin, based on Example 1, wherein the weights of p-methoxycinnamoyloxypropyltrimethoxysilane and 4-methyl-acrylate-2-hydroxybenzophenone in step 1) are set to 0.004 kg and 0.006 kg, respectively. Other conditions are the same as in Example 1.

[0027] Example 3 A method for preparing a radiation-resistant PVC resin is provided. Based on Example 1, the amount of the radiation-resistant agent in step 2) is set to 0.03 kg, and other conditions are the same as those in Example 1.

[0028] Example 4 A method for preparing a radiation-resistant PVC resin is provided. Based on Example 1, the amount of the radiation-resistant agent in step 2) is set to 0.001 kg, and other conditions are the same as those in Example 1.

[0029] Comparative Example 1 A method for preparing a radiation-resistant PVC resin is provided. Based on Example 1, no radiation-resistant agent is added in step 2), and other conditions are the same as those in Example 1.

[0030] Comparative Example 2 A method for preparing a radiation-resistant PVC resin, based on Example 1, wherein the amount of p-methoxycinnamoyloxypropyltrimethoxysilane in step 1) is set to 0.01 kg, 4-methyl-acrylate-2-hydroxybenzophenone is not added, and other conditions are the same as in Example 1.

[0031] Comparative Example 3 A method for preparing a radiation-resistant PVC resin, based on Example 1, wherein the amount of 4-methyl-acrylate-2-hydroxybenzophenone in step 1) is set to 0.01 kg, and p-methoxycinnamoyloxypropyltrimethoxysilane is not added, and other conditions are the same as in Example 1.

[0032] Comparative Example 4 A method for preparing a radiation-resistant PVC resin is provided, based on Example 1, wherein no radiation-resistant agent is added in step 2), but the radiation-resistant agent is added before adding the terminator in step 4), and the terminator is added after stirring for 8 minutes. Other conditions are the same as those in Example 1.

[0033] Performance Testing The PVC resins obtained in the above embodiments and comparative examples were respectively added with equal amounts of DOP, epoxy soybean oil, phosphite, antioxidant, stabilizer, and lubricant to prepare 2 mm thick square sheets. The PVC transparent square sheets were irradiated with 25 kGy high-energy rays for one week to simulate the irradiation sterilization scenario. The yellowness index and mechanical properties test results before irradiation are shown in Table 1.

[0034] The yellow index performance test method is based on HG / T 3862-2006.

[0035] The tensile strength and elongation at break performance test methods are based on GB / T 1040.1-2018, using type V specimens and a tensile speed of 50 mm / min.

[0036] Table 1 Test results before irradiation .

[0037] The yellowness index and mechanical properties test results after irradiation are shown in Table 2.

[0038] Table 2 Test results after irradiation .

[0039] The results show that the radiation-resistant additive solution can effectively delay the yellowing degree of PVC resin after 25kGy irradiation, especially in Example 1, the two reagents are used together to play a synergistic role, the yellow index after irradiation is the lowest, and the tensile strength and elongation at break are also significantly improved. Compared with the comparative example, the yellow index of the PVC product added with the radiation-resistant additive solution can be reduced by 5 to 7 after irradiation, and the preferred amount of the radiation-resistant additive solution added is 0.02 parts by weight.

[0040] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a radiation-resistant PVC resin, characterized in that: The following steps are involved: 1) Disperse the initiator, dispersant, radiation resistant agent and chain transfer agent evenly in water; 2) Evacuate to -0.9~-0.5MPa, add vinyl chloride monomer, stir evenly at room temperature, raise the temperature to 55~65℃, and react until the pressure reaches 0.2~0.3MPa; 3) Add the terminator, stir evenly, and dry to obtain PVC resin; Wherein, the radiation-resistant agent in step 1) is a solution of p-methoxycinnamoyloxypropyltrimethoxysilane and 4-methyl-acrylate-2-hydroxybenzophenone mixed in any proportion.

2. The method for preparing the radiation-resistant PVC resin according to claim 1, characterized in that: The weight ratio of p-methoxycinnamoyloxypropyltrimethoxysilane to 4-methyl-acrylate-2-hydroxybenzophenone in the radiation-resistant agent is 1:1-2.

3. The method for preparing the radiation-resistant PVC resin according to claim 1 or 2, characterized in that: The preparation method of the radiation-resistant agent comprises the following steps: dissolving p-methoxycinnamoyloxypropyltrimethoxysilane and 4-methyl-acrylate-2-hydroxybenzophenone in ethyl acetate to obtain a preliminary dispersion, adding sorbitan monooleate and sodium dodecylbenzene sulfonate, and stirring evenly to obtain the radiation-resistant agent.

4. The method for preparing the radiation-resistant PVC resin according to claim 3, characterized in that: The weight ratio of the preliminary dispersion to sorbitan monooleate and sodium dodecylbenzene sulfonate is 1:1-5:1-5.

5. The method for preparing the radiation-resistant PVC resin according to claim 3, characterized in that: The mixing is carried out uniformly by using a high-speed sand mill with a rotation speed of 5000-6000 rpm.

6. The method for preparing the radiation-resistant PVC resin according to claim 1, characterized in that: The usage of each raw material is as follows by weight: 100 parts of vinyl chloride monomer, 100-300 parts of deionized water, 0.005-0.2 parts of initiator, 0.005-0.2 parts of dispersant, 0.001-0.3 parts of radiation resistant agent and 0.01-0.05 parts of chain transfer agent.

7. The method for preparing the radiation-resistant PVC resin according to claim 6, characterized in that: It also includes 0.001 to 0.3 parts of a terminator.

8. The method for preparing the radiation-resistant PVC resin according to claim 1, characterized in that: The initiator is a mixture of tert-amyl peroxypivalate and tert-butyl peroxyneodecanoate in a weight ratio of 1:1-2; or a mixture of di(2-ethylhexyl) peroxydicarbonate and isopropylbenzene peroxyneodecanoate in a weight ratio of 1:1-2.

9. The method for preparing the radiation-resistant PVC resin according to claim 1, characterized in that: The dispersant is a mixture of hydroxypropyl methylcellulose E50, polyethanol PVA80 and polyethanol PVA55 in a weight ratio of 1:0.2-1:0.1-0.

5.

10. The method for preparing the radiation-resistant PVC resin according to claim 1, characterized in that: The drying is carried out by vacuum drying at 50-100° C. for 2-6 hours.