A process for the preparation of chlorinated polypropylene

Abstract

The application relates to a preparation method of chlorinated polypropylene, belonging to the technical field of polypropylene chlorination preparation. The water-phase suspension chlorination process belongs to heterogeneous chlorination, and the chlorination of polypropylene is uneven, and the solubility of the chlorinated polypropylene is poor. The polypropylene powder preparation method comprises the following steps: after polypropylene resin raw materials, degradation initiators and homogenizing agents are uniformly mixed, the polypropylene powder is prepared through extrusion granulation and liquid nitrogen powder grinding; wherein the degradation initiator is a mixture of one or more of aromatic peroxide, aliphatic peroxide and cyclic ketone peroxide in any proportion; and the homogenizing agent is a mixture of one or more of mineral oil, cyclohexanone and chlorinated hydrocarbon in any proportion. The degradation initiator is selected to cooperate with the homogenizing agent, the isotacticity and crystallinity of the polypropylene are damaged, the melt flow rate is reduced, the specific surface area and flowability are increased, the polypropylene is more easily chlorinated and deeply chlorinated, and therefore the uniformity of the polypropylene chlorination is improved.

Description

Technical Field

[0001] A method for preparing chlorinated polypropylene, belonging to the field of polypropylene chlorination preparation technology. Background Technology

[0002] Chlorinated polypropylene (CPP) is a chlorinated modified polypropylene product with a chlorine content that can be controlled between 20% and 65%. Because chlorine atoms are introduced into the molecular chain of polypropylene, it becomes a polar thermoplastic resin with excellent adhesion to polypropylene products. It also has good thermal stability, corrosion resistance, aging resistance, and wear resistance. It can be used as various adhesives for PP products, color carriers for inks and paints used in printing PP products, high-end inks, water-based coatings, and flame retardants for rubber and plastic products.

[0003] Currently, there are two main production processes for chlorinated polypropylene: the solvent method and the aqueous suspension method. In China, the solvent method is the dominant method. The advantages of the solvent-based chlorinated polypropylene process are simple process control, high chlorination uniformity, and good solubility. However, it requires large amounts of solvent, resulting in significant pollution and severe environmental damage. With increasing environmental awareness, the heavily polluting solvent-based chlorinated polypropylene production process will gradually be phased out and replaced by the green and environmentally friendly aqueous suspension chlorination process.

[0004] The aqueous suspension chlorination process involves suspending PP raw materials in an aqueous phase with the aid of a dispersant and stirring. An initiator is added, chlorine gas is introduced, and the mixture is heated to react. After the reaction, chlorinated polypropylene is obtained through processes such as deacidification, neutralization, washing, and drying. The aqueous suspension chlorination process is a heterogeneous chlorination process, resulting in uneven chlorination of polypropylene and poor solubility. Therefore, the aqueous suspension chlorination process needs to address the solubility problem of chlorinated polypropylene, which is essentially solving the problem of uniform chlorination of polypropylene. Besides being affected by the chlorination process itself, the uniformity of chlorination is mainly influenced by factors such as the isotacticity, crystallinity, melt index (molecular weight), particle size, and pretreatment method of the polypropylene raw material.

[0005] Patent CN1786037A discloses a method for producing chlorinated polypropylene using an aqueous suspension process, which involves pre-treating polypropylene or chlorinated polypropylene by swelling it in a solvent before chlorination. Patent CN103275251B discloses a method for preparing chlorinated polypropylene, which involves first swelling the polypropylene, then adding a lattice disruptor and an initiator, reacting the mixture in a solvent, adding an emulsifier and water for emulsification, filtering, washing with water, and drying to obtain polypropylene nanoparticles, which are then added to a mixed solution of trichloroethane and water for chlorination. However, this method uses a large amount of solvent, resulting in serious environmental problems in the later stages of treatment, making it unsuitable for widespread application.

[0006] Patent CN113527548A discloses a method for preparing highly chlorinated polypropylene using an aqueous suspension method, which employs pyrolyzed polypropylene wax powder. The use of pyrolyzed polypropylene wax powder is costly, with each ton of the raw material costing approximately 40,000 yuan, while the cost of polypropylene resin raw material is only 10,000 yuan per ton. Both the preparation method and cost are too high, making it unsuitable for long-term use. Furthermore, the molecular weight of the polypropylene wax is too small, affecting the product's adhesion strength and making it unsuitable for certain applications of chlorinated polypropylene, while also contributing to its high cost. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing chlorinated polypropylene that can effectively improve the chlorination uniformity of chlorinated polypropylene and whose process difficulty and raw material cost are suitable for practical applications.

[0008] The technical solution adopted by the present invention to solve its technical problem is: a method for preparing chlorinated polypropylene, wherein polypropylene powder and dispersant are dissolved in water, heated to the initiation temperature, an initiator is added, and chlorine gas is introduced for chlorination reaction to obtain the product, characterized in that: the method for preparing polypropylene powder includes the following steps: after polypropylene resin raw material is mixed evenly with degradation initiator and homogenizer, it is granulated by extrusion and ground by liquid nitrogen mill to obtain polypropylene powder. The degradation initiator is one or more of aromatic peroxides, aliphatic peroxides, and cyclic ketone peroxides in any proportion. The homogenizing agent is one or more of mineral oil, cyclohexanone, and chlorinated hydrocarbons in any proportion.

[0009] The preferred homogenizer does not react with the main components, but can disperse the degradation initiator evenly and prevent localized excessive degradation.

[0010] The main principle of the above preparation method is to improve the regularity and crystallinity of polypropylene resin raw materials: Based on the characteristics of aqueous suspension chlorination process and the factors affecting the performance of chlorinated polypropylene, this invention uses a chemical method, selecting a degradation initiator in combination with a homogenizing agent, to destroy the isotacticity and crystallinity of polypropylene, reduce the melt flow rate, and then deeply grind polypropylene into powder with liquid nitrogen, reducing the apparent density of polypropylene, increasing the specific surface area and fluidity, making polypropylene easier to chlorinate and deeply chlorinate, thereby improving the uniformity of polypropylene chlorination.

[0011] More preferably, the specific process of the chlorination reaction is as follows: after dissolving polypropylene powder and dispersant in water, the temperature is raised to 60~70℃ and kept at that temperature for 1~2 hours. Then, an initiator is added, and after evacuation, chlorine gas is introduced to carry out the chlorination reaction.

[0012] After heating to 60-70℃, keep warm for 1-2 hours to ensure that the polypropylene powder is fully and evenly dispersed in the water.

[0013] Preferably, the weight of the degradation initiator is 0.1 to 0.5% of the weight of the polypropylene resin raw material.

[0014] With the optimal dosage of degradation initiator, excessive degradation initiator can be avoided, which could lead to severe degradation and affect the adhesion in the later stages.

[0015] Preferably, the homogenizing agent is 0.5 to 1% of the weight of the polypropylene resin raw material.

[0016] The optimal amount of homogenizer can avoid the problem of low shear force and uneven particle size during extrusion granulation caused by excessive homogenizer dosage.

[0017] Preferably, the degradation initiator is dicumyl peroxide.

[0018] The preferred degradation initiator has a half-life that matches the chlorination reaction temperature, allowing it to be removed by half-life in subsequent processing.

[0019] Preferably, the homogenizing agent is mineral oil. It has a better compatibility with PP.

[0020] Preferably, the average particle size of the powder obtained by the liquid nitrogen grinding mill is no greater than 100 μm. Excessively large particle size may result in uneven chlorination, while excessively small particle size may prolong the grinding time.

[0021] Preferably, the polypropylene powder melt flow rate is 100~500g / 10min.

[0022] Low flow rate results in poor solubility, while high flow rate leads to low viscosity and low adhesion.

[0023] Preferably, the weight of the dispersant is 0.01 to 1% of the weight of the polypropylene powder.

[0024] Too little dispersant may not achieve the desired dispersing effect, while too much will affect chlorination and subsequent water treatment.

[0025] Preferably, the polypropylene resin raw material is homopolymer polypropylene with a melt flow rate of 20~40g / 10min.

[0026] The preferred melt flow rate works better with the above preparation method. Too high a melt flow rate may lead to over-grinding, while too low a melt flow rate may reduce the chlorination uniformity of the final polypropylene powder.

[0027] Preferably, the chlorination reaction is carried out at a temperature of 80-100°C and a pressure of no more than 0.5 MPa.

[0028] Under the above preparation method conditions, the preferred reaction conditions can ensure that a more uniformly chlorinated polypropylene resin is obtained.

[0029] Compared with existing technologies, the beneficial effects of this invention are as follows: The main principle of the above-mentioned preparation method is to improve the regularity and crystallinity of polypropylene resin raw materials. Based on the characteristics of the aqueous suspension chlorination process and the factors affecting the performance of chlorinated polypropylene, this invention employs a chemical method, using a degradation initiator in conjunction with a homogenizing agent, to disrupt the isotacticity and crystallinity of polypropylene. After reducing the melt flow rate, the polypropylene is then cryogenically ground into powder using liquid nitrogen, reducing the apparent density of polypropylene, increasing its specific surface area and fluidity, making it easier to chlorinate and deeply chlorinate, thereby improving the uniformity of polypropylene chlorination. Detailed Implementation

[0030] The present invention will be further described below with reference to the embodiments, of which Embodiment 3 is the preferred embodiment.

[0031] In the following examples and comparative examples, the polypropylene resins PPH-Y30 and EPE30R in the raw materials are homopolymer polypropylene resin products from Qilu Petrochemical Company, with melt flow rates of 24~38 g / 10min and 20~30 g / 10min, respectively. Example

[0032] A method for preparing chlorinated polypropylene, the preparation methods in Examples 1-3 and Examples 7-9 include the following steps: 1) Polypropylene resin raw materials, degradation initiators, and homogenizers are added to a high-speed mixer and mixed evenly. The mixture is then extruded and water-cooled at 180℃~200℃ to obtain polypropylene resin granules. The obtained polypropylene resin granules are then ground into powder with a specific average particle size using a low-temperature liquid nitrogen mill to obtain polypropylene powder.

[0033] 2) Take 10 kg of polypropylene powder obtained in step 1) and 50 L of deionized water, add them to a 100 L enamel reactor, add 700 g of 6 wt% polyvinyl alcohol solution and 10 g of sodium polyacrylate, stir to make the polypropylene powder uniformly suspended in the aqueous phase.

[0034] 3) Heat to 60~70℃ and hold for 1 hour. Add 80g of benzoyl peroxide initiator, evacuate the reactor to remove air, and introduce chlorine gas to start the reaction. Heat to 90℃ at a rate of 2℃ / min, and control the chlorine flow rate to 100~200g / min to maintain the pressure inside the reactor at 0.5Mpa. The total chlorine flow rate is 20kg. After reaching the required chlorine flow rate, evacuate the reactor to remove chlorine gas, cool the reactor to 50℃, and then deacidify, neutralize, wash, and dry to obtain chlorinated polypropylene.

[0035] In the preparation method of Example 4, step 2) of the polyvinyl alcohol solution was replaced with a 3wt% polyvinyl alcohol solution, and sodium polyacrylate was set to 30g. Other conditions were the same as in Examples 1-3.

[0036] In the preparation method of Example 5, based on the preparation method of Example 4, the total chlorine flow rate in step 3) is set to 25 kg, and other conditions are the same as in Example 1.

[0037] In the preparation method of Example 6, based on the preparation method of Example 4, the total chlorine flow rate in step 3) is set to 10 kg, and other conditions are the same as in Example 1.

[0038] The polypropylene resin raw materials, degradation initiators and homogenizers used in each embodiment, the dosage of each component, the melt flow rate after grinding of polypropylene powder particles, and the particle size of polypropylene powder obtained in step 1) are shown in Table 1 below.

[0039] Table 1 Raw materials for the examples .

[0040] Comparative Example 1 A method for preparing chlorinated polypropylene, based on the preparation method of Example 1, but without using a degradation initiator and a homogenizing agent, step 1) is set as follows: 1) Polypropylene resin raw materials are directly ground into powder with an average particle size of less than 100μm using a low-temperature liquid nitrogen grinding mill.

[0041] Other conditions are the same as in Example 1.

[0042] Comparative Example 2 A method for preparing chlorinated polypropylene, based on the preparation method of Example 1, except that no homogenizing agent is added in step 1), and other conditions are the same as in Example 1.

[0043] Comparative Example 3 A method for preparing chlorinated polypropylene, based on the preparation method of Example 1, except that step 1) does not add a degradation initiator, and other conditions are the same as in Example 1.

[0044] Comparative Example 4 A method for preparing chlorinated polypropylene, based on the preparation method of Example 1, in step 1), the low-temperature liquid nitrogen grinding mill is replaced with an ordinary resin grinding mill. During the grinding process, the polypropylene resin raw material exhibits severe agglomeration and adhesion, oxidation and deterioration, and cannot be used.

[0045] Performance testing The chlorinated polypropylene obtained in the above examples and comparative examples was subjected to performance tests. The chlorination time, appearance, chlorine content (according to GB / T 7139-2002), and solubility in a 20% toluene solution were compared and analyzed. In the solubility test, higher clarity indicates better chlorination uniformity of the chlorinated polypropylene resin, with a slightly yellow appearance being optimal. The test results are shown in Table 2 below.

[0046] Table 2 Performance Test Results .

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing chlorinated polypropylene, comprising: dissolving polypropylene powder and a dispersant in water, heating to an initiation temperature of 60-70°C, adding an initiator, and then introducing chlorine gas to react and obtain chlorinated polypropylene, characterized in that... The method for preparing polypropylene powder includes the following steps: after the polypropylene resin raw material is mixed evenly with the degradation initiator and the homogenizing agent, it is then extruded and granulated, and ground with a liquid nitrogen mill to obtain polypropylene powder. The degradation initiator is one or more of aromatic peroxides, aliphatic peroxides, and cyclic ketone peroxides in any proportion. The homogenizing agent is mineral oil.

2. The method for preparing chlorinated polypropylene according to claim 1, characterized in that: The degradation initiator is 0.1 to 0.5% of the weight of the polypropylene resin raw material.

3. The method for preparing chlorinated polypropylene according to claim 1, characterized in that: The homogenizing agent is 0.5 to 1% of the weight of the polypropylene resin raw material.

4. The method for preparing chlorinated polypropylene according to claim 1, characterized in that: The average particle size of the powder obtained by the liquid nitrogen grinding mill is no greater than 100 μm.

5. The method for preparing chlorinated polypropylene according to claim 1, characterized in that: The melt flow rate of the polypropylene powder is 100~500g / 10min.

6. The method for preparing chlorinated polypropylene according to claim 1, characterized in that: The weight of the dispersant is 0.01 to 1% of the weight of the polypropylene powder.

7. The method for preparing chlorinated polypropylene according to claim 1, characterized in that: The polypropylene resin raw material is homopolymer polypropylene with a melt flow rate of 20~40g / 10min.

8. The method for preparing chlorinated polypropylene according to claim 1, characterized in that: The chlorination reaction is carried out at a temperature of 80-100°C and a pressure of no more than 0.5 MPa.