A polypropylene hot melt adhesive

Abstract

The present invention discloses a polypropylene hot melt adhesive. The polypropylene hot melt adhesive comprises a grafted resin and a toughening resin; wherein the grafted resin comprises a base resin and a grafting agent, and the base resin comprises one or a combination of two or more selected from homopolypropylene, block polypropylene, and random polypropylene; the grafting agent comprises glycidyl methacrylate, an antioxidant, and a cross-linking agent; and the toughening resin comprises ethylene-octene copolymer and polyethylene. The present invention also discloses a method for preparing a polypropylene hot melt adhesive and a polypropylene heat shrinkable tape. The polypropylene hot melt adhesive provided by the present invention has the advantages of good fluidity, greater tensile strength and elongation at break, higher temperature resistance, better high-temperature peel strength and shear strength, good anti-corrosion and sealing performance, good waterproof performance, simple preparation process, and low production cost.

Description

Technical Field

[0001] The invention relates to a polypropylene hot melt adhesive, and also relates to a preparation method of the polypropylene hot melt adhesive, in particular to a pipeline patching anti-corrosion polypropylene heat shrinkable tape using the polypropylene hot melt adhesive. Background Art

[0002] Existing oil and gas pipelines generally utilize a high-temperature transportation mode, which increases the temperature of the transport medium to reduce its viscosity. This is particularly true during crude oil transportation, where temperatures can reach temperatures exceeding 100°C. Such high temperatures place severe strain on pipelines. Polyolefin heat-shrinkable tape patching technology provides a safeguard for high-temperature pipeline transportation. Corrosion protection technologies for oil and gas pipelines, both domestically and internationally, typically utilize a three-layer polyolefin anti-corrosion coating system, specifically consisting of a base layer of fused epoxy powder, a middle layer of adhesive, and an outermost layer of polyolefin.

[0003] Commonly used polyolefin heat shrinkable tapes include polyethylene heat shrinkable tapes and polypropylene heat shrinkable tapes. Generally, the operating temperature of polyethylene heat shrinkable tapes is slightly lower and is not suitable for the above-mentioned high-temperature transport pipelines. Polypropylene heat shrinkable tapes are considered to be heat shrinkable tape products with excellent construction efficiency and anti-corrosion effects. The polypropylene hot melt adhesive in the polypropylene heat shrinkable tape is a key component. It not only has to have a high bonding strength to the epoxy primer and the polypropylene coating, but also has to ensure a long-lasting sealing effect under long-term high-temperature operating conditions. In some existing studies, polypropylene hot melt adhesives are usually modified. One known method is to add ethylene-vinyl acetate copolymer (EVA) and maleic anhydride to the polypropylene primer. It is believed that the addition of ethylene-vinyl acetate copolymer can effectively improve the bonding strength of polypropylene, and the addition of maleic anhydride, on the one hand, forms activation points with polyolefins for grafting reaction, and on the other hand, generates activation points with ethylene-vinyl acetate copolymer, which ultimately increases the crystallinity, that is, reduces the viscosity of the overall product, making the hot melt adhesive more easily adhere to the substrate to be bonded, thereby improving the bonding strength.

[0004] Although the addition of maleic anhydride and ethylene-vinyl acetate copolymer to modify polypropylene solves the shortcomings of polypropylene hot melt adhesive, such as poor fluidity and poor mechanical properties, it also brings new problems. First, the water barrier properties of the modified polypropylene hot melt adhesive are poor, which has drawbacks in its use in the high-humidity southern and coastal areas. Second, maleic anhydride-modified polypropylene has a high melt index, severe late-stage degradation, and a fast crystallization rate. Once crystallized, it loses its bonding ability, requiring rapid construction. Otherwise, it will have a negative impact on the bonding effect. The existence of the above problems has caused certain troubles to the construction party, so it is still necessary to improve the existing polypropylene hot melt adhesive to solve the defects caused by the use of maleic anhydride while providing good bonding strength. Summary of the Invention

[0005] In order to solve the deficiencies in the prior art, the present invention aims to provide a new polypropylene hot melt adhesive, comprising a grafted resin and a toughening resin.

[0006] The grafting resin includes a base resin and a grafting agent. The base resin includes one or more selected from homopolypropylene, block polypropylene, and random polypropylene. Preferably, based on the total weight of the base resin as 100%, the block polypropylene and random polypropylene are each independently present in an amount of 0-100%. The grafting agent includes glycidyl methacrylate, an antioxidant, and a crosslinking agent. The antioxidant is selected from one or two of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol and tris[2,4-di-tert-butylphenyl]phosphite. The crosslinking agent is selected from one or more selected from diisopropyl benzene peroxide, benzoyl peroxide, bis(tert-butylperoxyisopropyl)benzene, and tert-butyl peroxyacetate. Preferably, the crosslinking agent is selected from diisopropyl benzene peroxide.

[0007] The toughening resin comprises ethylene-octene copolymer and polyethylene. As a preferred embodiment, the melt index of the ethylene-octene copolymer is 5-10 g / 10 min. As another preferred embodiment, the melt index of the polyethylene is 1.5-5 g / 10 min.

[0008] More specifically, the present invention provides a polypropylene hot melt adhesive comprising, by weight, 60%-70% of a grafted resin, 5%-10% of an ethylene-octene copolymer, and 20%-30% of polyethylene. In the grafted resin, the base resin and grafting agent have a weight ratio of 100:1 to 100:2. A ratio below this can easily lead to a low grafting rate, which can affect bond strength, while a ratio above this can cause side reactions such as excessive crosslinking or degradation. The grafting agent comprises, by weight, 55%-65% of glycidyl methacrylate, 15%-20% of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 10%-15% of tris[2,4-di-tert-butylphenyl]phosphite, and 10%-15% of dicumyl peroxide.

[0009] Another object of the present invention is to provide a method for preparing a polypropylene hot melt adhesive, comprising: (1) uniformly mixing a base resin and a grafting agent in a ratio of 100:1-100:2, extruding the base resin through a twin-screw extruder at a screw speed of 80-200 r / min, melting the grafting reaction in a melting zone at 185°C-200°C, and pelletizing the grafted resin through a pelletizer to obtain a grafted resin; (2) uniformly mixing the grafted resin and a toughening resin composed of an ethylene-octene copolymer and polyethylene, extruding the grafted resin through a single-screw extruder at a screw speed of 100-200 r / min, melting the grafted resin in a melting zone at 195°C-205°C, and pelletizing the grafted resin through a pelletizer to obtain the polypropylene hot melt adhesive.

[0010] The third object of the present invention is to provide a polypropylene heat shrinkable tape made from the polypropylene hot melt adhesive.

[0011] A fourth object of the present invention is to provide a method for preparing a polypropylene heat-shrinkable tape, comprising: extruding the polypropylene hot melt adhesive through a single-screw extruder at a screw speed of 50-70 r / min, melting it in a melting zone of 195°C-205°C, and extrusion coating it on a heat-shrinkable polypropylene substrate that has been irradiated and cross-linked to produce a polypropylene heat-shrinkable tape.

[0012] Compared with the prior art, the polypropylene hot melt adhesive of the present invention has the following beneficial effects:

[0013] (1) Compared with conventional polypropylene hot melt adhesives, the polypropylene hot melt adhesive provided by the present invention has the advantages of good fluidity, greater tensile strength and elongation at break, higher temperature resistance, better high-temperature peel strength and shear strength, and good anti-corrosion sealing performance. It is suitable for patching the three-layer polypropylene outer anti-corrosion layer.

[0014] (2) The present invention avoids the use of maleic anhydride and ethylene-vinyl acetate copolymer modification systems that have poor usability in high-humidity and harsh environments, and innovatively proposes a highly hydrophobic modification system of glycidyl methacrylate, ethylene-octene copolymer, and polyethylene. The polypropylene hot melt adhesive prepared by this system is more resistant to hydrolysis than conventional polypropylene hot melt adhesives.

[0015] (3) The preparation method of the polypropylene hot melt adhesive and the polypropylene heat shrinkable tape provided by the present invention does not require special processes and can be put into production in ordinary factories. The production cost is low, which is conducive to the rapid innovation of technology in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the components and preparation process of the polypropylene hot melt adhesive according to an embodiment of the present invention;

[0017] Figure 2 The figure is a schematic diagram of the principle of the preparation process of the polypropylene heat shrinkable tape according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings. The following embodiments are only intended to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. The technical solutions of the embodiments of the present invention are further illustrated by several typical application examples. The scope of protection of the present invention shall be subject to the definition of the claims.

[0019] Examples 1-15

[0020] The polypropylene hot melt adhesive of this embodiment includes a grafted resin and a toughening resin. The grafted resin includes a base resin and a grafting agent, and the toughening resin includes ethylene-octene copolymer and polyethylene. The base resin includes segmented polypropylene and / or random polypropylene. The grafting agent includes glycidyl methacrylate, an antioxidant, and a crosslinking agent. The antioxidant includes pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris[2,4-di-tert-butylphenyl]phosphite. The crosslinking agent includes dicumyl peroxide.

[0021] The weight percentages of the various components are shown in Table 1 below. The weight percentages of segmented polypropylene and random polypropylene are based on the total weight of the base resin as 100%. The weight percentages of glycidyl methacrylate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris[2,4-di-tert-butylphenyl]phosphite, and dicumyl peroxide are based on the total weight of the grafting agent as 100%. The weight percentages of the grafted resin, ethylene-octene copolymer, and polyethylene in the polypropylene hot melt adhesive are based on the total weight of the polypropylene hot melt adhesive as 100%.

[0022] Table 1

[0023]

[0024]

[0025] The performance of the polypropylene hot melt adhesives of Examples 1-15 was tested, and the test results of various performance indicators are shown in Table 2 below:

[0026] Table 2

[0027]

[0028] In Examples 1 to 15, segmented polypropylene and / or random polypropylene are the base resins of the hot melt adhesive, which are mainly used to improve the heat resistance of the hot melt adhesive, are suitable for the transportation of high-temperature oil and gas pipelines, and provide strong adhesion to the polypropylene substrate. With glycidyl methacrylate as the grafting monomer, ethylene-octene copolymer (melt index of 5-10g / 10min) and polyethylene (melt index of 1.5-5g / 10min) are used as toughening resins. First, the crystallinity of the polypropylene hot melt adhesive is increased, the viscosity of the polypropylene hot melt adhesive is reduced, the product is easier to flow, and the toughness of the product is also improved. Second, a high hydrophobic modification system suitable for polypropylene hot melt adhesive is provided. The polypropylene hot melt adhesive prepared by this system is more resistant to hydrolysis than conventional polypropylene hot melt adhesive. Tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester is a commonly used antioxidant in this field. It is used in combination with tris[2.4-di-tert-butylphenyl] phosphite and is mainly used to improve product life and delay material aging. Dicumyl peroxide is used as a cross-linking agent mainly to increase the grafting rate of glycidyl methacrylate on the base resin.

[0029] It can be seen from the data in Table 2 that the polypropylene hot melt adhesive provided in the embodiment of the present invention has the advantages of good fluidity, greater tensile strength and elongation at break, higher temperature resistance, better high-temperature peel strength and shear strength, and good anti-corrosion sealing performance compared with conventional polypropylene hot melt adhesive. It is suitable for patching the three-layer polypropylene outer anti-corrosion layer.

[0030] Example 16

[0031] like Figure 1 As shown, Example 16 of the present invention also provides a preparation method of the above-mentioned polypropylene hot melt adhesive, comprising the following steps: (1) preparing and mixing the base resin and the grafting agent in a ratio of 100:1-100:2, extruding through a twin-screw extruder at a screw speed of 80-200 r / min, melting and grafting in a melting zone at 185°C-200°C, and pelletizing through a pelletizer to obtain a grafted resin; (2) preparing and mixing the grafted resin and a toughening resin composed of an ethylene-octene copolymer and polyethylene, extruding through a single-screw extruder at a screw speed of 100-200 r / min, melting in a melting zone at 195°C-205°C, and pelletizing through a pelletizer to obtain the polypropylene hot melt adhesive.

[0032] Example 17

[0033] like Figure 2As shown, Example 17 of the present invention also provides a method for preparing a polypropylene heat shrinkable tape using the polypropylene hot melt adhesive prepared by the above method, comprising: extruding the prepared polypropylene hot melt adhesive through a single-screw extruder with a screw speed of 50-70r / min, melting it in a melting zone of 195°C-205°C, calendering and coating it on a heat shrinkable polypropylene substrate that has been cross-linked by radiation, and cutting and forming it to obtain a polypropylene heat shrinkable tape.

[0034] The preparation method of the polypropylene hot melt adhesive and the polypropylene heat shrinkable tape provided by the present invention does not require special processes and can be put into production in ordinary factories. The production cost is low, which is conducive to the rapid innovation of technology in this field.

[0035] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A polypropylene hot melt adhesive, characterized in that: The polypropylene hot melt adhesive comprises a grafting resin and a toughening resin; wherein: the grafting resin comprises a base resin and a grafting agent, the base resin comprising one or a combination of two or more selected from homopolypropylene, block polypropylene, and random polypropylene; the grafting agent comprises glycidyl methacrylate, an antioxidant, and a crosslinking agent; the toughening resin comprises ethylene-octene copolymer and polyethylene; The antioxidant is selected from one or two of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol and tris[2,4-di-tert-butylphenyl]phosphite; the cross-linking agent is selected from one or a combination of two or more of dicumyl peroxide, benzoyl peroxide, bis(tert-butylperoxyisopropyl)benzene, and tert-butyl peroxyacetate; The melt index of the ethylene-octene copolymer is 5-10 g / 10 min; the melt index of the polyethylene is 1.5-5 g / 10 min; The polypropylene hot melt adhesive comprises, by weight percentage, 60%-70% of a grafted resin, 5%-10% of an ethylene-octene copolymer, and 20%-30% of polyethylene; In the grafted resin, the ratio of the base resin to the grafting agent is 100:1-100:2 by weight.

2. The polypropylene hot melt adhesive according to claim 1, characterized in that: The grafting agent comprises, by weight percentage, 55%-65% of glycidyl methacrylate, 15%-20% of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 10%-15% of tris[2,4-di-tert-butylphenyl]phosphite, and 10%-15% of dicumyl peroxide.

3. The method for preparing a polypropylene hot melt adhesive according to claim 1 or claim 2, characterized in that: The following steps are involved: (1) The base resin and the grafting agent are mixed uniformly in a ratio of 100:1-100:2, extruded through a twin-screw extruder at a screw speed of 80-200 r / min, melted in a melting zone at 185°C-200°C for grafting reaction, and pelletized by a pelletizer to obtain a grafted resin; (2) The grafted resin and a toughening resin composed of an ethylene-octene copolymer and polyethylene are mixed uniformly, extruded through a single-screw extruder at a screw speed of 100-200 r / min, melted in a melting zone at 195°C-205°C, and pelletized by a pelletizer to obtain the polypropylene hot melt adhesive.

4. A polypropylene heat shrinkable tape using the polypropylene hot melt adhesive according to claim 1 or claim 2.

5. A method for preparing the polypropylene heat shrinkable tape according to claim 4, characterized in that: The following steps are involved: The polypropylene hot melt adhesive is extruded through a single screw extruder at a screw speed of 50-70 r / min, melted in a melting zone of 195° C.-205° C., and extrusion-coated on a heat-shrinkable polypropylene substrate that has been irradiated and cross-linked to produce a polypropylene heat-shrinkable tape.

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