Production process of random copolymer soft fiber high-end sanitary material special material

Abstract

This invention provides a production process for a high-end sanitary material made of random copolymer soft fiber, which mainly solves the problems of coarse filaments, numerous burrs, and poor softness of existing gas-phase homopolymer polypropylene materials. The process is characterized by the following steps: S1: Prepolymerization reaction: Prepolymerizing a catalyst with propylene to generate a prepolymer product; S2: Random copolymerization reaction: Under the action of a catalyst, the generated prepolymer product undergoes a random copolymerization reaction with gas-phase propylene and a small amount of ethylene to obtain a polymer base powder under polymerization conditions; S3: Peroxide degradation reaction: The obtained polymer base powder is then blended with additives, degraded by an oxide degrading agent, and melt-extruded and granulated to obtain the target product. This production process for a high-end sanitary material made of random copolymer soft fiber results in nonwoven fabric products with good softness, finer and more uniform filament diameter, and a superior hand feel.

Description

Technical Field

[0001] This invention relates to the field of olefin polymerization, and in particular to a production process for a high-end sanitary material made of random copolymer soft fiber. Background Technology

[0002] Industrially, the main methods for producing high-flow-rate polypropylene (PP) for nonwoven fabrics using the gas-phase process are the hydrogen conditioning method and the degradation method (also known as the controlled rheology method). The hydrogen conditioning method involves adding a certain amount of hydrogen during propylene polymerization to adjust the relative molecular mass and distribution of polypropylene, producing polypropylene with a higher melt flow rate. The degradation method involves first polymerizing propylene into a powder with a lower melt flow rate, then adding liquid or solid peroxides for degradation, followed by extrusion granulation to obtain a polypropylene product with a higher melt flow rate and a narrower relative molecular mass distribution. After degradation, the molecular weight distribution of polypropylene becomes narrower, enhancing the spinnability of the fiber material. Therefore, the gas-phase production of fiber-grade high melt flow rate polypropylene uses the degradation method, achieved by degrading homopolymer polypropylene with oxides. When subsequently processed into nonwoven fabric, the spun filaments are relatively coarse, resulting in insufficient softness in the finished product, necessitating the addition of softeners and other additives to improve processing and performance.

[0003] Currently, the raw material used in high-end nonwoven sanitary materials produced by fumed-phase polymerization (FRP) in China (such as baby diapers, adult diapers, surgical gowns, and operating room supplies) is polypropylene homopolymer. This produces relatively coarse filaments, with a drawing diameter limited to approximately 2 denier. Consequently, the finished products lack sufficient softness and exhibit burrs, causing skin irritation and affecting the feel. This invention addresses the shortcomings of FRP homopolymer, including coarse filaments, numerous burrs, and poor softness. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the problems of coarse filaments, numerous burrs, and poor softness of existing gas-phase homopolymer polypropylene materials in the background art. Instead, it provides a production process for a high-end sanitary material made of random copolymer soft fiber. The nonwoven fabric products made from this random copolymer soft fiber have good softness, which is more than 15% higher than that of traditional homopolymer products. At the same time, the diameter of the filaments is finer and more uniform, solving the problem of burrs and resulting in a better hand feel.

[0005] The present invention solves its problem through the following technical solution: the production process of this random copolymer soft fiber high-end sanitary material includes the following steps:

[0006] Step 1: Prepolymerization reaction

[0007] The catalyst is prepolymerized with propylene to generate a prepolymerized product under prepolymerization reaction conditions.

[0008] Step 2: Random copolymerization reaction

[0009] Under the action of a catalyst, the generated prepolymer product is randomly copolymerized with gaseous propylene and ethylene to obtain polymer base powder under the polymerization process conditions.

[0010] Step 3: Peroxide degradation reaction

[0011] The obtained polymer base powder is then blended with additives, degraded by an oxide degrading agent, the melt index of the product is adjusted, and the target product is obtained by melt extrusion granulation.

[0012] Furthermore, in steps 1 and 2, the catalyst is composed of a main catalyst, a co-catalyst, and an electron donor; the main catalyst is ZN118 and / or CS2, the co-catalyst is triethylaluminum, and the electron donor is DonorC.

[0013] Furthermore, in steps 1 and 2, the ratio of the main catalyst ZN118 to CS2 is 1:1; the ratio of the co-catalyst to the catalyst is 3-5:1; and the ratio of the co-catalyst to the electron donor is 2-10:1.

[0014] Furthermore, the catalyst for the prepolymerization reaction needs to be prepared under nitrogen protection, mixed with oil and pre-contacted at 15°C before entering the prepolymerization reactor, where it undergoes a prepolymerization reaction with propylene that has entered through an online mixer; the oil is a mixture of white oil and petrolatum at a volume ratio of 2:1.

[0015] Furthermore, the prepolymerization reaction process conditions are as follows: prepolymerization is carried out in a propylene liquid phase bulk environment, in a small loop at a temperature of 25℃-30℃ and a pressure of 2.8Mpa-3.2Mpa, with a residence time of 10-20 minutes.

[0016] Furthermore, the polymerization conditions for the random copolymerization reaction in step 2 are as follows: temperature 70℃-75℃, pressure 2.7MPa-3.0MPa, residence time 1 hour 20 minutes; co-catalyst to catalyst ratio 3-5:1, co-catalyst to electron donor ratio 2-10:1 (TEAL / CAT 3-5, TEAL / Donor 2-10); ethylene content controlled at 2.0%-3.0% (mass percentage); hydrogen is added to the multi-zone circulating reactor to adjust the molecular weight, ensuring that the melt flow index (MFR) of the random copolymer polypropylene powder generated in the reactor is 7.0-10.0 g / 10 min.

[0017] Furthermore, in step 3, the additive antioxidant system is a composite antioxidant (B215 and calcium stearate compound antioxidant), with an addition amount of 1000ppm-2000ppm; the added degradation agent is 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane, also known as TRIGONOX101.

[0018] Furthermore, in step 3, the additives are single agents, namely IRGANOX 1010 additive, IRGANOX 168 additive and calcium stearate, which are compounded in a mass ratio of 1:2:2.

[0019] Furthermore, the target product granules generated in step 3 have a melt index of 35.0-40.0 g / 10 min.

[0020] Furthermore, the target product generated in step 3 is used to prepare high-end nonwoven sanitary materials. The special nonwoven fabric products are more than 15% softer than traditional homopolymer products.

[0021] The reaction mechanism of the production process of the random copolymer soft fiber high-end sanitary material of this invention:

[0022] This invention relates to a high-end sanitary material made from random copolymer soft fibers. The material is produced by randomly copolymerizing fumed propylene and fumed ethylene, embedding ethylene into a long-chain polypropylene structure, blending with additives, undergoing oxide degradation, and then melt extrusion granulation to obtain the target product. The catalyst system (CAT) consists of a Ziegler-Natta type catalyst and its support, formulated with the co-catalyst triethylaluminum (TEAL-Triethylaluminum). The electron donor, DonorC (cyclohexylmethyldimethoxysilane), is a liquid silane used as a co-catalyst to adjust the isotactic stereochemistry of the high-efficiency catalyst. Excessive addition will reduce catalyst activity; polymerization using only the high-efficiency catalyst will result in a product with a high content of random polymers. Unlike isotactic polymers, random polymers have high viscosity. A small amount of atactic material in the finished product helps prevent embrittlement and improves impact strength. The content of atactic material in the final product is controlled by the amount of electron donor added.

[0023] Compared with the above-mentioned background technology, the present invention has the following beneficial effects:

[0024] This invention relates to a production process for a high-end random copolymer soft fiber material specifically for sanitary materials. The material is produced by randomly copolymerizing fumed propylene and fumed ethylene, embedding ethylene into a long-chain polypropylene structure. This is followed by blending with additives, oxide degradation, and melt extrusion granulation to obtain the target product. The ethylene content is controlled at 2.0%-3.0%. The resulting nonwoven fabric exhibits superior softness, exceeding that of traditional homopolymer products by more than 15%, giving it an irreplaceable advantage in the field of silky soft sanitary materials. Furthermore, the finer and more uniform fiber diameter eliminates the problem of burrs, resulting in a superior hand feel. Detailed implementation method:

[0025] The present invention will be further described below with reference to specific embodiments:

[0026] The production process of this random copolymer soft fiber high-end sanitary material includes the following steps:

[0027] Step 1: Prepolymerization reaction

[0028] The catalyst and propylene were prepolymerized at a temperature of 25℃-30℃ and a pressure of 2.8Mpa-3.2Mpa for a residence time of 10-20 minutes to generate a prepolymerized product.

[0029] The catalyst used is composed of a main catalyst, a co-catalyst, and an electron donor; the main catalyst is ZN118 and / or CS2, the co-catalyst is triethylaluminum, and the electron donor is DonorC (cyclohexylmethyldimethoxysilane), a liquid silane, which is used to adjust the isotacticity of the high-efficiency catalyst.

[0030] The ratio of the main catalyst (CAT) ZN118 to CS2 is 1:1; the ratio of the co-catalyst to the main catalyst is 3-5:1; and the ratio of the co-catalyst to the electron donor is 2-10:1.

[0031] Step 2: Random copolymerization reaction

[0032] Under the action of a catalyst, the generated prepolymer product is subjected to random copolymerization with gaseous propylene and a small amount of ethylene. The polymerization process conditions are: temperature 70℃-75℃, pressure 2.7MPa-3.0MPa, residence time 1 hour 20 minutes, TEAL / CAT 3-5, TEAL / Donor 2-10, and ethylene content controlled at 2.0%-3.0% (mass percentage). Hydrogen is added to the multi-zone circulating reactor to adjust the molecular weight, ensuring that the melt index (also known as melt mass flow rate, MFR) of the random copolymer polypropylene generated in the reactor is 7.0-10.0 g / 10 min, thus obtaining the polymer base powder.

[0033] Step 3: Peroxide degradation reaction

[0034] The obtained polymer base powder is then blended with additives, degraded by oxides, and melt-extruded into granules to obtain the target product.

[0035] The additive is a compound antioxidant of B215 and calcium stearate, or a single-agent compound of IRGANOX 1010 additive, IRGANOX 168 additive and calcium stearate in a mass ratio of 1:2:2, with an addition amount of 1000ppm-2000ppm.

[0036] The peroxide degrading agent used in the oxide degradation process is 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane, also known as TRIGNOX 101. Its function is to degrade the polymer chains generated during polymerization. The addition amount is 350ppm-550ppm, controlling the product melt index to 35.0-40.0 g / 10min. The main process adjustment in the granulation section of this invention is to maintain the cylinder temperature between 240℃ and 260℃ and the melt temperature between 200℃ and 230℃.

[0037] Example 1

[0038] The propylene polymerization reaction is carried out on a polypropylene unit, utilizing the Spherizone process polymerization control technology and employing a multi-zone circulating reactor. The main equipment includes a prepolymerization reactor, a multi-zone circulating reactor, and an extrusion granulator.

[0039] (1) First step: Prepolymerization reaction

[0040] The catalyst requires three agents: main catalyst (CAT) ZN118 + CS2 (ratio 1:1), co-catalyst TEAL (triethylaluminum), and electron donor Donor C.

[0041] The catalyst needs to be prepared under nitrogen protection, mixed with oil (white oil and petrolatum, volume ratio 2:1), pre-contacted at 15°C, and then fed into the prepolymerization reactor to react with propylene that has entered through an online mixer to produce a prepolymerized product.

[0042] Prepolymerization is carried out in a propylene liquid phase bulk environment, in a small loop at a temperature of 25℃-30℃ and a pressure of 2.8Mpa-3.2Mpa, with a residence time of 10-20 minutes.

[0043] (2) Second step: random copolymerization reaction

[0044] The prepolymerized powder was subjected to random copolymerization with gaseous propylene and a small amount of ethylene in a multi-zone circulating reactor to obtain polymer powder.

[0045] The polymerization process conditions are: temperature 70℃-75℃, pressure 2.7MPa-3.0MPa, residence time 1 hour 20 minutes, TEAL / CAT ratio 3-5:1, TEAL / Donor ratio 2-10:1, and ethylene content controlled at 2.0%-3.0% (mass percentage). Hydrogen is added to the multi-zone circulating reactor to adjust the molecular weight, ensuring that the melt flow rate (MFR) of the generated random copolymer polypropylene is 7.0-10.0 g / 10 min, yielding polymer powder.

[0046] (3) Third step: Peroxide degradation reaction

[0047] The unreacted catalyst in the polymer powder was removed by hot nitrogen and then dried to obtain the treated polymer base powder. The antioxidant additive system consisted of a compound antioxidant of B215 and calcium stearate, added at a rate of 1000ppm-2000ppm; the degradation agent was TRIGNOX 101 peroxide, added at a rate of 350ppm-550ppm, adjusting the melt index of the product to 35.0-40.0 g / 10min. Granulation was performed using a twin-screw extruder, with the amount of degradation agent adjusted according to the melt index of the polymer powder and the melt index requirements of the final granulated product. Process parameters and the physical properties of the obtained polymer product are shown in Tables 1 and 2.

[0048] Example 2

[0049] The prepolymerization and random copolymerization reaction conditions, additive formulation, and dosage in Example 2 were the same as in Example 1. The difference from Example 1 was that imported ZN118 catalyst was used. Process parameters and the physical properties of the resulting polymer product are shown in Tables 1 and 2.

[0050] Example 3

[0051] The catalyst, prepolymerization, and polymerization process conditions used in Example 3 were the same as in Example 1. The difference from Example 1 was the type and amount of additives. The powder obtained from polymerization contained IRGANOX 1010 additive, IRGANOX 168 additive, and calcium stearate in a ratio of 1:2:2, and the degradation agent was TRIGONOX 101 (Nouryon Functional Chemicals BV, Netherlands).

[0052] Comparative Example 1

[0053] The existing gas-phase method for producing high-flowability nonwoven PP uses the same catalyst and prepolymerization as in Example 2. The difference lies in the second step of Comparative Example 1, which is a homopolymerization reaction without ethylene. Hydrogen is added to adjust the molecular weight, ensuring that the melt flow index (MFR) of the homopolymer polypropylene generated in the reactor is 2.4-3.6 g / 10 min, yielding a polymer base powder. Due to the low melt flow index of the base powder, a larger amount of degradation agent is needed to obtain the polypropylene granules with the desired melt flow index. The process parameters and the physical properties of the resulting polymer products are shown in Tables 1 and 2.

[0054] The polymer data in Examples 1-3 and Comparative Example 1 were obtained using the following test methods:

[0055] ①Melt mass flow rate (MFR): Determined according to the method described in GB / T3682-2000; measured using a CEAST 7026 melt flow indexer at 230℃ and a load of 2.16 kg.

[0056] ②Tensile strength: Determined according to the method described in GB / T1040-2006 using a ZWICK BT1-FR005TN.A50 universal testing machine;

[0057] ③ Flexural modulus: determined according to the method described in GB / T9341-2008; using a ZWICK BT1-FR005TN.A50 universal testing machine;

[0058] ④ Impact strength: Tested according to the method described in GB / T1843-2008, using ZWICK's BPI-5.5STAC.

[0059] ⑤ Oxidation induction period: Determined according to the method described in GB / T2951.1-1994. Using a Q20 DSC instrument from Waters China Co., Ltd., 10±0.5mg of sample was heated to 200℃ at a rate of 20℃ / min under nitrogen protection, held at the temperature for 5min, then nitrogen was stopped and oxygen was introduced at a flow rate of 50mL / min.

[0060] ⑥ Melting point / crystallization temperature: Determined according to the method described in GB / T 19466-2004. Using a Q20 DSC from Waters China Ltd., under N2 protection at a flow rate of 50 ml / min, 5 ± 0.5 mg of sample was first heated from room temperature to 200 °C at a heating rate of 10 °C / min and held at that temperature for 5 min to eliminate thermal history. Then, the sample was cooled to 40 °C at a cooling rate of 10 °C / min and held at that temperature for 5 min. Finally, the sample was heated to 200 °C again at a heating rate of 10 °C / min.

[0061] ⑦ Ash content: determined according to the method described in GB / T9345.1;

[0062] ⑧ Vinyl groups; determined according to the method described in SN / T3298-2012;

[0063] ⑨ Yellow Index: Determined according to the method described in HG / T 3862-2006 using a yellow index meter from HUNTERLAB.

[0064] Table 1. Process parameters of the examples

[0065]

[0066] Table 2. Results of polymer property analysis in the examples

[0067]

[0068] As shown in Table 2, the random copolymer polypropylene product prepared by the production process of the random copolymer soft fiber high-end sanitary material of the present invention, compared with the various indicators of existing products, shows that due to the addition of a small amount of ethylene and optimization of ethylene distribution, the flexural modulus and melting point of the polypropylene product are reduced, which increases the good spinning performance and the softness of the nonwoven fabric.

[0069] The high-end nonwoven sanitary products (baby diapers, adult diapers, surgical gowns, and operating room supplies) prepared using the special materials of this invention have excellent softness, exceeding that of traditional homopolymer products by more than 15%, giving them an irreplaceable advantage in the field of silky sanitary products. Simultaneously, the filaments are finer and more uniform in diameter, solving the problem of burrs and resulting in a superior feel to the finished products.

[0070] The raw materials and components used in the above embodiments are all commercially available.

[0071] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Therefore, the content of the present invention is not limited to the embodiments listed, and any equivalent modifications made to the technical solutions of the present invention by those skilled in the art through reading the present invention specification are covered by the claims of the present invention.

Claims

1. A production process for a high-end sanitary material made of random copolymer soft fiber, characterized in that: Includes the following steps: Step 1: Prepolymerization reaction The catalyst is prepolymerized with propylene to generate a prepolymerized product under prepolymerization reaction conditions. Step 2: Random copolymerization reaction Under the action of a catalyst, the generated prepolymer product is randomly copolymerized with gaseous propylene and ethylene to obtain polymer base powder under the polymerization process conditions. Step 3: Peroxide degradation reaction The obtained polymer base powder is then blended with additives, degraded by an oxide degrading agent, the melt index of the product is adjusted, and the target product is obtained by melt extrusion granulation. In steps 1 and 2, the catalyst is composed of a main catalyst, a co-catalyst, and an electron donor; the main catalyst is ZN118 and / or CS2, the co-catalyst is triethylaluminum, and the electron donor is DonorC. The polymerization conditions for the random copolymerization reaction in step 2 are as follows: temperature 70℃-75℃, pressure 2.7MPa-3.0MPa, residence time 1 hour 20 minutes; the ratio of co-catalyst to main catalyst is 3-5:1, and the ratio of co-catalyst to electron donor is 2-10:1; the mass percentage of polymerized ethylene is controlled at 2.0%-3.0%; hydrogen is added to the multi-zone circulating reactor to adjust the molecular weight, ensuring that the melt index of the random copolymer polypropylene powder generated in the reactor is 7.0-10.0 g / 10 min. In step 3, the additive is a composite antioxidant, which is a combination of B215 and calcium stearate, with an addition amount of 1000ppm-2000ppm; the added degradation agent is 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane.

2. The production process of the high-end sanitary material made of random copolymer soft fiber according to claim 1, characterized in that: In steps 1 and 2, the ratio of the main catalyst ZN118 to CS2 is 1:1; the ratio of the co-catalyst to the main catalyst is 3-5:1; and the ratio of the co-catalyst to the electron donor is 2-10:

1.

3. The production process of the high-end sanitary material made of random copolymer soft fiber according to claim 1, characterized in that: The catalyst for the prepolymerization reaction needs to be prepared under nitrogen protection, mixed with oil and pre-contacted at 15°C before entering the prepolymerization reactor, where it undergoes a prepolymerization reaction with propylene that has entered through an online mixer; the oil is a mixture of white oil and petrolatum at a volume ratio of 2:

1.

4. The production process of the high-end sanitary material made of random copolymer soft fiber according to claim 1, characterized in that: The prepolymerization reaction process conditions are as follows: prepolymerization is carried out in a propylene liquid phase bulk environment, in a small loop at a temperature of 25℃-30℃ and a pressure of 2.8Mpa-3.2Mpa, with a residence time of 10-20 minutes.

5. The production process of the high-end sanitary material made of random copolymer soft fiber according to claim 1, characterized in that: In step 3, the additives are single agents, namely IRGANOX 1010, IRGANOX 168 and calcium stearate, which are compounded in a mass ratio of 1:2:

2.

6. The production process of the high-end sanitary material made of random copolymer soft fiber according to claim 1, characterized in that: The target product granules generated in step 3 have a melt index of 35.0-40.0 g / 10 min.

7. The production process of the high-end sanitary material made of random copolymer soft fiber according to claim 1 or 6, characterized in that: The target product generated in step 3 is used to prepare high-end nonwoven sanitary materials; the high-end nonwoven sanitary materials are baby diapers, adult diapers, and surgical gowns.

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