Hot melt adhesive for sealing of vehicle lamps and method of preparation

Abstract

The application provides a hot melt adhesive for sealing of a vehicle lamp, characterized in that raw material components include, in terms of mass fractions, 10-30 parts of a styrene thermoplastic elastomer, 5-15 parts of a metallocene polypropylene, 10-30 parts of a random polyolefin, 30-40 parts of a petroleum resin, 15-25 parts of a rosin resin, 5-15 parts of a polyisobutylene, and 0.1-1 part of an antioxidant. The hot melt adhesive has good spreading performance and initial adhesion strength, and can be quickly cooled and condensed after being attached to a lamp shell of the vehicle lamp, so that the lamp shell of the vehicle lamp is bonded and fixed and has high strength.

Description

Technical Field

[0001] This invention belongs to the field of hot melt adhesive preparation, specifically relating to a hot melt adhesive for sealing automotive lights and its preparation method. Background Technology

[0002] Hot melt adhesive is a solvent-free thermoplastic adhesive prepared by melt blending thermoplastic polymers as the base material and tackifiers, viscosity modifiers, plasticizers, antioxidants, and fillers as modifiers. At room temperature, hot melt adhesive is a 100% solid, highly elastic state. In use, it is heated and melted to a low-viscosity viscous flow state, then uniformly applied to the bonding interface of the adherends. After cooling and curing, the van der Waals forces at the bonding interface and its own cohesive forces tightly bond the adherends. Compared with traditional inorganic and solvent-based adhesives, hot melt adhesive has advantages such as water resistance, fast curing speed, and the ability to be bonded multiple times. Furthermore, in actual production, it is easy to process, recyclable, highly automated, and low-cost, giving it broad application prospects.

[0003] In the process of manufacturing automotive headlights, the structure of the headlight is as shown in the attached diagram. Figure 1 As shown (lens 1, bulb 2, reflector 3, lamp housing 4, adhesive 5), the lens is inserted into the lamp housing. To ensure a tight connection between the lens (glass or PC material) and the lamp housing (PP, PBT, ABS, etc.), adhesive must be used for bonding and sealing. High requirements are placed on the adhesive. First, it must be heat-resistant. When a car is driven with its lights on for extended periods, the internal temperature of the lamp can reach 70-160℃. The adhesive will be affected by the heat emitted by the bulb; therefore, the adhesive must ensure that its bonding and sealing performance remains unchanged at such high temperatures and that it does not release organic gases or cause fogging. Second, the lamp housing is exposed to sunlight for long periods, so it must prevent the adhesive layer from cracking or aging after prolonged use. Finally, the adhesive must withstand long-term erosion from atmospheric moisture and rainwater without affecting its bonding and sealing performance.

[0004] Currently, polyurethane hot melt adhesive (PUR) is commonly used for sealing automotive headlight housings. It is made from a single-component, solvent-free prepolymer with terminal isocyanate groups and appropriate additives. Its main component is a prepolymer with terminal isocyanate groups synthesized from polyols and diisocyanates. PUR has good initial tack strength and curing time, but the production cost and selling price of PUR adhesive are high, which leads to higher costs for automotive headlight assembly. Polyurethane AB adhesive, also known as two-component mixed curing adhesive, consists of one component as the adhesive and the other as a curing agent. The two components can be mixed and cured without relying on temperature for curing. However, AB adhesive is complicated to operate, requiring the mixing of two components before use, and the workpiece can only be moved after the adhesive has cured, resulting in lower production efficiency. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a hot melt adhesive for sealing vehicle lamp housings and its preparation method.

[0006] This invention provides a hot melt adhesive for sealing vehicle lights, the raw material components of which, by mass parts, include 10-30 parts of styrene-based thermoplastic elastomer, 5-15 parts of metallocene polypropylene, 10-30 parts of random polyolefin, 30-40 parts of petroleum resin, 15-25 parts of rosin resin, 5-15 parts of polyisobutylene, and 0.1-1 parts of antioxidant.

[0007] Preferably, the styrene-based thermoplastic elastomer is a polystyrene-isoprene-styrene resin, and the diblock content of the styrene-based thermoplastic elastomer is 10%-50%.

[0008] Preferably, the diblock content of the styrene-based thermoplastic elastomer is 20%-40%.

[0009] Preferably, it comprises 15-25 parts of styrene-based thermoplastic elastomer, 5-10 parts of metallocene-catalyzed polypropylene, 10-20 parts of random polyolefin, 30-40 parts of petroleum resin, 15-25 parts of rosin resin, 5-15 parts of polyisobutylene, and 0.1-1 parts of antioxidant.

[0010] Preferably, the mixture also includes terpene phenol resin, wherein the terpene phenol resin comprises 5-10 parts by weight.

[0011] Preferably, the petroleum resin is one or more of C5 petroleum resin, C9 petroleum resin, or C5 / C9 copolymer petroleum resin.

[0012] Preferably, the antioxidant is an aromatic amine antioxidant.

[0013] Preferably, it also includes 10-20 parts of styrene-butadiene-styrene resin.

[0014] The present invention also provides a method for preparing the hot melt adhesive for sealing vehicle lights as described above, comprising the following steps:

[0015] Step 1: Preheat the reactor;

[0016] Step 2: Add polyisobutylene into the reactor, raise the temperature inside the reactor to 180°C and keep stirring at a speed of 20-50 r / min until the polyisobutylene is completely melted, and keep the temperature constant at 180°C.

[0017] Step 3: According to the viscosity of the raw materials from low to high, add metallocene polypropylene and random polyolefin in sequence, melt them one by one, maintain the stirring speed of 20-50 r / min until the above raw materials are completely melted, and keep the temperature constant at 180℃.

[0018] Step 4: Melt the styrene-based thermoplastic elastomer outside the reactor, and then introduce the molten styrene-based thermoplastic elastomer into the reactor, maintaining a stirring speed of 20-40 r / min and keeping the temperature constant at 180℃.

[0019] Step 5: Add petroleum resin, rosin resin and antioxidant in sequence, maintain the stirring speed at 10-30 r / min, and after stirring evenly, extrude it into the outlet to form a mold.

[0020] Preferably, when adding styrene-butadiene-styrene resin, the styrene-butadiene-styrene resin and styrene-based thermoplastic elastomer are heated and melted outside the reactor, and then the molten mixture is introduced into the reactor.

[0021] In this invention, polyisobutylene acts as a viscosity and open time regulator, exhibiting good flowability and dispersibility; metallocene polypropylene demonstrates good elasticity and low-temperature resistance; random polyolefins possess excellent surface wetting and spreading properties, while also exhibiting good compatibility with petroleum resins; petroleum resins and rosin resins serve as tackifiers, effectively improving the product's adhesion and elastomer compatibility; a small amount of antioxidant can alleviate material aging during heating, extending the product's lifespan in daily use.

[0022] Compared with the prior art, the hot melt adhesive provided by the present invention has the following beneficial effects:

[0023] 1. The hot melt adhesive provided by this invention has good spreading performance and initial tack strength. After being bonded to the car lamp housing, it can cool and solidify quickly, bonding and fixing the car lamp housing with high strength.

[0024] 2. The preparation and application methods of the hot melt adhesive provided by this invention are relatively simple, with high production and application efficiency. It can bond and set in a very short time during use, achieving low cost.

[0025] 3. The hot melt adhesive provided by this invention has good high temperature resistance, solvent resistance and water resistance, and a long service life. In addition, the hot melt adhesive also has the property of product repairability by heating. It can be recycled or repaired by melting at high temperature, thus reducing losses. Attached Figure Description

[0026] The above and other objects, features, and advantages of the invention will become clearer through a more detailed description of the preferred embodiments illustrated in the accompanying drawings. The same reference numerals denote the same parts throughout the drawings, and the drawings are not intentionally drawn to scale with actual dimensions; the focus is on illustrating the gist of the invention.

[0027] Figure 1 This is a schematic diagram of a vehicle headlight sealing structure in the prior art. Detailed Implementation

[0028] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0029] This invention provides a hot melt adhesive for sealing vehicle lights, the raw material components of which, by mass parts, include 10-30 parts of styrene-based thermoplastic elastomer, 5-15 parts of metallocene polypropylene, 10-30 parts of random polyolefin, 30-40 parts of petroleum resin, 15-25 parts of rosin resin, 5-15 parts of polyisobutylene, and 0.1-1 parts of antioxidant.

[0030] Furthermore, styrene-based thermoplastic elastomers are polystyrene-isoprene-styrene resins (SIS resins), and the diblock content of styrene-based thermoplastic elastomers is 10%-50%. Diblock content refers to the proportion of polymers composed of the same monomer at both ends in a block copolymer to the total mass of the copolymer. The diblock content of block copolymers has a significant impact on the polymer's thermal stability, mechanical properties, and physicochemical properties. In block copolymers, different structural types can be classified according to the proportion of block units composed of different monomers. Taking polystyrene-isoprene-styrene resin as an example, it is an ABA-terminal copolymer configuration, where A represents block 1 and B represents block 2, meaning that the two ends connected are composed of the same monomer units, while the intermediate monomer units are different monomer units.

[0031] In a preferred embodiment, the diblock content of the styrene-based thermoplastic elastomer is 20%-40%.

[0032] In a preferred embodiment, the mixture comprises 15-25 parts of styrene-based thermoplastic elastomer, 5-10 parts of metallocene-catalyzed polypropylene, 10-20 parts of random polyolefin, 30-40 parts of petroleum resin, 15-25 parts of rosin resin, 5-15 parts of polyisobutylene, and 0.1-1 parts of antioxidant.

[0033] In a preferred embodiment, the adhesive further includes 5-10 parts by weight of terpene phenol resin. Terpene phenol resin is a resin polymerized from terpene resin and phenol. It has good polarity and can be integrated with most film-forming substances. This improves the extensibility and flexibility of the adhesive, thereby enhancing its quality.

[0034] In this embodiment, the petroleum resin is one or more of C5 petroleum resin, C9 petroleum resin, or C5 / C9 copolymer petroleum resin. Petroleum resin and rosin resin are added to the formulation as tackifying resins. These resins improve the wettability of the hot melt adhesive to the substrate, ensuring thorough contact and bonding between the hot melt adhesive and the headlight housing and lens, thereby increasing bond strength, improving the adhesive's impact resistance and peel strength, extending service life, and reducing creep. Furthermore, petroleum resin and rosin resin impart good initial tack to the hot melt adhesive.

[0035] In this embodiment, the antioxidant is an aromatic amine antioxidant. During the reaction, the aromatic amine antioxidant participates in the oxidation reaction by donating hydrogen atoms, generating intermediates and further undergoing coupling reactions to scavenge free radicals during the reaction process.

[0036] In a preferred embodiment, the mixture further comprises 10-20 parts of styrene-butadiene-styrene resin (SBS resin). The diblock content of the SBS resin is 15%-20%.

[0037] This invention also provides a method for preparing the above-mentioned hot melt adhesive for sealing vehicle lights, comprising the following steps:

[0038] Step 1: Preheat the reactor;

[0039] Step 2: Add polyisobutylene into the reactor, raise the temperature inside the reactor to 180°C and keep stirring at a speed of 20-50 r / min until the polyisobutylene is completely melted, and keep the temperature constant at 180°C.

[0040] Step 3: According to the viscosity of the raw materials from low to high, add metallocene polypropylene and random polyolefin in sequence, melt them one by one, maintain the stirring speed of 20-50 r / min until the above raw materials are completely melted, and keep the temperature constant at 180℃.

[0041] Step 4: Melt the styrene-based thermoplastic elastomer outside the reactor, and then introduce the molten styrene-based thermoplastic elastomer into the reactor, maintaining a stirring speed of 20-40 r / min and keeping the temperature constant at 180℃.

[0042] Step 5: Add petroleum resin, rosin resin and antioxidant in sequence, maintain the stirring speed at 10-30 r / min, and after stirring evenly, extrude it into the outlet to form a mold.

[0043] Furthermore, when styrene-butadiene-styrene resin is added, the styrene-butadiene-styrene resin and styrene-based thermoplastic elastomer are heated and melted outside the reactor, and then the molten mixture is introduced into the reactor.

[0044] The following specific embodiments and comparative examples will be used to illustrate the details.

[0045] Example 1

[0046] By weight, it includes 10 parts polystyrene-isoprene-styrene resin, 5 parts metallocene polypropylene, 10 parts random polyolefin, 30 parts petroleum resin, 15 parts rosin resin, 5 parts polyisobutylene, and 0.5 parts antioxidant, wherein the diblock content of polystyrene-isoprene-styrene resin is 10%.

[0047] Preparation method:

[0048] Step 1: Preheat the reactor;

[0049] Step 2: Add polyisobutylene into the reactor, raise the temperature inside the reactor to 180°C and keep stirring at a stirring speed of 30 r / min until the polyisobutylene is completely melted, and keep the temperature constant at 180°C.

[0050] Step 3: According to the viscosity of the raw materials from low to high, add metallocene polypropylene and random polyolefin in sequence, melt them one by one, maintain the stirring speed of 30 r / min until the above raw materials are completely melted, and keep the temperature constant at 180℃.

[0051] Step 4: Heat and melt the polystyrene-isoprene-styrene resin outside the reactor, and introduce the molten polystyrene-isoprene-styrene resin into the reactor, maintaining a stirring speed of 30 r / min and a constant temperature of 180℃.

[0052] Step 5: Add petroleum resin, rosin resin and antioxidant in sequence, maintain the stirring speed at 20 r / min, and after stirring evenly, extrude the mixture into the outlet to form a mold.

[0053] Example 2

[0054] By weight, it includes 10 parts polystyrene-isoprene-styrene resin, 5 parts metallocene polypropylene, 10 parts random polyolefin, 30 parts petroleum resin, 15 parts rosin resin, 5 parts polyisobutylene, and 0.5 parts antioxidant, wherein the diblock content of polystyrene-isoprene-styrene resin is 30%.

[0055] The preparation method is the same as in Example 1.

[0056] Example 3

[0057] By weight, it includes 10 parts polystyrene-isoprene-styrene resin, 5 parts metallocene polypropylene, 10 parts random polyolefin, 30 parts petroleum resin, 15 parts rosin resin, 5 parts polyisobutylene, and 0.5 parts antioxidant, wherein the diblock content of polystyrene-isoprene-styrene resin is 50%.

[0058] The preparation method is the same as in Example 1.

[0059] Example 4

[0060] By weight, it includes 15 parts polystyrene-isoprene-styrene resin, 5 parts metallocene polypropylene, 10 parts random polyolefin, 30 parts petroleum resin, 15 parts rosin resin, 5 parts polyisobutylene, and 0.5 parts antioxidant, wherein the diblock content of polystyrene-isoprene-styrene resin is 30%.

[0061] The preparation method is the same as in Example 1.

[0062] Example 5

[0063] By weight, it includes 25 parts of polystyrene-isoprene-styrene resin, 5 parts of metallocene polypropylene, 10 parts of random polyolefin, 30 parts of petroleum resin, 15 parts of rosin resin, 5 parts of polyisobutylene, and 0.5 parts of antioxidant, wherein the diblock content of polystyrene-isoprene-styrene resin is 30%.

[0064] The preparation method is the same as in Example 1.

[0065] Example 6

[0066] By weight, it includes 10 parts of polystyrene-isoprene-styrene resin, 10 parts of styrene-butadiene-styrene resin, 5 parts of metallocene polypropylene, 10 parts of random polyolefin, 30 parts of petroleum resin, 15 parts of rosin resin, 5 parts of polyisobutylene, and 0.5 parts of antioxidant, wherein the diblock content of polystyrene-isoprene-styrene resin is 30%.

[0067] Preparation method:

[0068] Step 1: Preheat the reactor;

[0069] Step 2: Add polyisobutylene into the reactor, raise the temperature inside the reactor to 180°C and keep stirring at a stirring speed of 30 r / min until the polyisobutylene is completely melted, and keep the temperature constant at 180°C.

[0070] Step 3: According to the viscosity of the raw materials from low to high, add metallocene polypropylene and random polyolefin in sequence, melt them one by one, maintain the stirring speed of 30 r / min until the above raw materials are completely melted, and keep the temperature constant at 180℃.

[0071] Step 4: Heat and melt the polystyrene-isoprene-styrene resin and styrene-butadiene-styrene resin outside the reactor, and introduce the molten polystyrene-isoprene-styrene resin and styrene-butadiene-styrene resin into the reactor, maintain the stirring speed at 30 r / min, and keep the temperature constant at 180℃.

[0072] Step 5: Add petroleum resin, rosin resin and antioxidant in sequence, maintain the stirring speed at 20 r / min, and after stirring evenly, extrude the mixture into the outlet to form a mold.

[0073] Comparative Example 1

[0074] By weight, it includes 5 parts metallocene polypropylene, 10 parts random polyolefin, 30 parts petroleum resin, 15 parts rosin resin, 5 parts polyisobutylene, and 0.5 parts antioxidant.

[0075] The preparation method is the same as in Example 1.

[0076] Comparative Example 2

[0077] By weight, it includes 50 parts of polystyrene-isoprene-styrene resin, 5 parts of metallocene polypropylene, 10 parts of random polyolefin, 30 parts of petroleum resin, 15 parts of rosin resin, 5 parts of polyisobutylene, and 0.5 parts of antioxidant, wherein the diblock content of polystyrene-isoprene-styrene resin is 10%.

[0078] The preparation method is the same as in Example 1.

[0079] Comparative Example 3

[0080] By weight, it includes 10 parts polystyrene-isoprene-styrene resin, 5 parts metallocene polypropylene, 10 parts random polyolefin, 30 parts petroleum resin, 15 parts rosin resin, 5 parts polyisobutylene, and 0.5 parts antioxidant, wherein the diblock content of polystyrene-isoprene-styrene resin is 60%.

[0081] The performance of the hot melt adhesives or hot melt adhesives prepared in Examples 1-6 and Comparative Examples 1-3 was tested. The test items and results are as follows:

[0082] 1. Viscosity testing method

[0083] Viscosity was determined according to GB / T 2794-2013 "Determination of Viscosity of Adhesives - Single-Cylinder Rotation Viscometer Method", and the results were recorded in centipoises (cps).

[0084] 2. Ring initial tack test: The test was conducted in accordance with the national standard GB / T31125-2014, and the results were recorded in N / inch.

[0085] 3. Tensile strength test method: The test object is the hot melt adhesive after application.

[0086] Tensile strength was determined in accordance with GB / T 1040.1-2018 "Determination of tensile properties of plastics - Part 1: General rules", and the results were recorded in MPa.

[0087] 4. 180° peel strength test: The test shall be conducted in accordance with the provisions of the national standard GB / T2792-2014, and the results shall be recorded in N / inch.

[0088] 5. Hazardous substance content testing: The testing will be conducted by a third-party testing and inspection service unit, including testing for cadmium, lead, mercury, hexavalent chromium, polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PSDEs), phthalates (such as dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), and diisobutyl phthalate (DIBP)), to determine whether they comply with the limits required by the EU RoHS Directive 2011 / 65 / EU Annex II Amendment Directive (EU) 2015 / 863.

[0089] 6. Softening point test method: The test object is untreated hot melt adhesive.

[0090] The test was conducted according to GB / T15332-1994 "Ring and Ball Method for Determining the Softening Point of Hot Melt Adhesives", and the results were recorded in degrees Celsius (°C).

[0091] The test results for the above test items are as follows:

[0092] Table 1: Summary Table of Hot Melt Adhesive Performance Test Data from Examples

[0093]

[0094] As shown in Table 1, the diblock content of polystyrene-isoprene-styrene resin in the hot melt adhesives prepared in Examples 1-3 of this invention gradually increased, while other components and preparation methods remained the same. The data in Table 1 shows that with the increase of diblock content in the SIS resin, the viscosity gradually decreased, while the initial tack gradually increased, and the softening point, peel strength, and tensile strength fluctuated, first increasing and then decreasing. In Examples 2, 4, and 5, the amount of SIS resin gradually increased, while other components and preparation methods remained the same. It can be seen that with the increase of SIS resin amount, the viscosity, softening point, initial tack, peel strength, and tensile strength of the hot melt adhesive all increased, but the increase in peel strength and tensile strength with the increase of SIS resin amount was not significant. In Examples 2 and 6, styrene-butadiene-styrene resin was added as an elastomer. A comparison shows that after adding SBS resin, the viscosity, softening point, and initial tack of the hot melt adhesive increased, but the peel strength and tensile strength decreased slightly.

[0095] Table 2: Summary Table of Performance Test Data for Comparative Hot Melt Adhesives

[0096]

[0097]

[0098] Table 2 summarizes the data from Comparative Examples 1-3, which are compared to Example 1. Comparative Example 1 did not add SIS resin, but all other components and preparation methods were the same as in Example 1. Table 2 shows that without SIS resin, the viscosity, initial tack, and peel strength were also low. Comparative Example 2 added an excessive amount of SIS resin to Example 1. It can be seen that the viscosity of the hot melt adhesive increased significantly, and other performance indicators also increased markedly. However, due to the excessively high viscosity, the surface properties of the hot melt adhesive were sticky in actual use, easily attracting dust or other small objects. Comparative Example 3 replaced the low diblock content SIS resin with a high diblock content SIS resin to the one used in Example 1. It can be seen that the viscosity of the hot melt adhesive prepared with the high diblock content SIS resin was too low.

[0099] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A hot melt adhesive for sealing automotive lights, characterized in that, Its raw material components, by mass parts, include 10-30 parts of styrene thermoplastic elastomer, 5-15 parts of metallocene polypropylene, 10-30 parts of random polyolefin, 30-40 parts of petroleum resin, 15-25 parts of rosin resin, 5-15 parts of polyisobutylene, and 0.1-1 parts of antioxidant. The styrene-based thermoplastic elastomer is a polystyrene-isoprene-styrene resin, and the diblock content of the styrene-based thermoplastic elastomer is 10%-50%.

2. The hot melt adhesive for sealing vehicle lights as described in claim 1, characterized in that, The diblock content of the styrene-based thermoplastic elastomer is 20%-40%.

3. The hot melt adhesive for sealing vehicle lights as described in claim 1, characterized in that, It includes 15-25 parts of styrene-based thermoplastic elastomer, 5-10 parts of metallocene-catalyzed polypropylene, 10-20 parts of random polyolefin, 30-40 parts of petroleum resin, 15-25 parts of rosin resin, 5-15 parts of polyisobutylene, and 0.1-1 parts of antioxidant.

4. The hot melt adhesive for sealing vehicle lights as described in claim 1, characterized in that, It also includes terpene phenol resin, which is 5-10 parts by mass.

5. The hot melt adhesive for sealing vehicle lights as described in claim 1, characterized in that, The petroleum resin is one or more of C5 petroleum resin, C9 petroleum resin, or C5 / C9 copolymer petroleum resin.

6. The hot melt adhesive for sealing vehicle lights as described in claim 1, characterized in that, The antioxidant is an aromatic amine antioxidant.

7. The hot melt adhesive for sealing vehicle lights as described in claim 1, characterized in that, It also includes 10-20 parts of styrene-butadiene-styrene resin.

8. A method for preparing a hot melt adhesive for sealing vehicle lights as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Preheat the reactor; Step 2: Add polyisobutylene into the reactor, raise the temperature inside the reactor to 180°C and keep stirring at a speed of 20-50 r / min until the polyisobutylene is completely melted, and keep the temperature constant at 180°C. Step 3: According to the viscosity of the raw materials from low to high, add metallocene polypropylene and random polyolefin in sequence, melt them one by one, maintain the stirring speed of 20-50 r / min until the above raw materials are completely melted, and keep the temperature constant at 180℃. Step 4: Melt the styrene-based thermoplastic elastomer outside the reactor, and then introduce the molten styrene-based thermoplastic elastomer into the reactor, maintaining a stirring speed of 20-40 r / min and keeping the temperature constant at 180℃. Step 5: Add petroleum resin, rosin resin and antioxidant in sequence, maintain the stirring speed at 10-30 r / min, and after stirring evenly, extrude it into the outlet to form a mold.

9. The method for preparing the hot melt adhesive for sealing vehicle lights as described in claim 8, characterized in that, When styrene-butadiene-styrene resin is added, the styrene-butadiene-styrene resin and styrene-based thermoplastic elastomer are heated and melted outside the reactor, and then the molten mixture is introduced into the reactor.

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