Yellowing-resistant polyvinylidene fluoride heat shrink tube and preparation method thereof

Abstract

The invention discloses an anti-yellowing polyvinylidene fluoride heat shrink tube. The anti-yellowing polyvinylidene fluoride heat shrink tube is prepared from polyvinylidene fluoride resin and sarin resin. By adding surlyn resin, on one hand, surlyn resin serving as a cationic polymer can consume hydrofluoric acid, the yellowing phenomenon of polyvinylidene fluoride resin in the processing and using processes can be effectively reduced, generation of a conjugated structure in a polyvinylidene fluoride resin structure is reduced, and the yellowing phenomenon of the appearance of a product is reduced; on the other hand, as the nucleating agent, the transparency and flexibility of the material can be improved, and wide application of the polyvinylidene fluoride material is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of material improvement, and in particular to a yellowing-resistant polyvinylidene fluoride heat shrinkable tube and a preparation method thereof. Background Art

[0002] Polyvinylidene fluoride (PVDF for short) is a linear, semi-crystalline polymer whose polymer chain structure is mainly composed of repeated monomer units - [CH2CF2] - connected head to tail. It mainly refers to vinylidene fluoride homopolymer or copolymer of vinylidene fluoride and other small amounts of fluorine-containing vinyl monomers. It has the characteristics of both fluororesins and general resins, and has good chemical corrosion resistance, high temperature resistance, oxidation resistance, weather resistance, radiation resistance, etc. The melting point of polyvinylidene fluoride is lower than that of most fluoroplastics, about 165-172°C, so its processing temperature is also low, comparable to polyolefins. In the past half century, it has been widely used in outdoor decorative films and coatings, corrosion-resistant equipment, and flame-retardant electronic insulation.

[0003] However, polyvinylidene fluoride resin has poor thermal stability during melt processing. During thermoplastic processing such as injection molding or extrusion, the product tends to turn yellow and dark, and its transparency decreases. This phenomenon is very common in the processing and manufacturing of PVDF resin and is generally called "yellowing". This yellowing phenomenon affects the appearance of the product and greatly limits the widespread application of PVDF materials. Summary of the invention

[0004] Aiming at the problem that the yellowing phenomenon of polyvinylidene fluoride resin in the processing and manufacturing process in the prior art causes poor overall application effect, the present invention provides a yellowing-resistant polyvinylidene fluoride heat shrinkable tube.

[0005] The above object of the present invention is achieved through the following technical solutions:

[0006] In a first aspect of the present invention, a yellowing-resistant polyvinylidene fluoride heat shrinkable tube is provided. The yellowing-resistant polyvinylidene fluoride heat shrinkable tube preparation material comprises the following raw materials in parts by weight:

[0007] 100 parts of polyvinylidene fluoride resin;

[0008] 2 to 10 parts of sarling resin.

[0009] In some embodiments, the yellowing-resistant polyvinylidene fluoride heat shrinkable tube preparation material further includes the following raw materials: 0.5 to 3 parts of NOR-type hindered amine stabilizer.

[0010] In some embodiments, the NOR hindered amine stabilizer is a unimolecular N-alkoxy hindered amine stabilizer.

[0011] In some embodiments, the polyvinylidene fluoride is copolymerized polyvinylidene fluoride.

[0012] In some embodiments, the copolymerized polyvinylidene fluoride has a melt index of 1 to 15 g / 10 min (230° C. / 5 kg) and a melt viscosity of 500 to 2500 Pa·s (230° C., 100 s -1 ).

[0013] In some embodiments, the sarling resin is at least one of ethylene-(meth)acrylic acid zinc salt, sodium salt, and lithium salt ion bond polymers.

[0014] In some embodiments, the yellowing-resistant polyvinylidene fluoride heat shrinkable tube preparation material further includes the following raw materials: 0.1 to 2 parts of a cross-linking sensitizer.

[0015] In some embodiments, the crosslinking sensitizer is at least one of trimethallyl isocyanate and its derivatives, triallyl cyanurate and its derivatives, tripropargyl cyanurate and its derivatives, trimethylolpropane trimethacrylate and its derivatives, and trimethylolpropane triacrylate and its derivatives.

[0016] The second aspect of the present invention provides a method for preparing the above-mentioned yellowing-resistant polyvinylidene fluoride heat shrinkable tube, comprising the following steps:

[0017] Masterbatch processing: polyvinylidene fluoride resin and surin resin are mixed evenly, extruded, drawn and pelletized by extrusion equipment to obtain masterbatch particles;

[0018] Extrusion into pipe: Extruding the masterbatch particles obtained above into pipes through an extrusion device to obtain semi-finished pipes;

[0019] Irradiation process: irradiate the semi-finished pipes through irradiation equipment, control the irradiation dose to 5-15 Mrad, and obtain irradiated pipes;

[0020] Expansion molding: the irradiated tube is expanded, cooled, and formed to obtain a yellowing-resistant polyvinylidene fluoride heat shrinkable tube.

[0021] In some embodiments, in the masterbatch processing step, when the polyvinylidene fluoride resin and the surin resin are mixed, at least one of a NOR-type hindered amine stabilizer and a cross-linking sensitizer is also added for mixing;

[0022] Or, in the extrusion tube forming step, the extrusion temperature of the extrusion equipment is 180-250°C;

[0023] Or, in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 8-40;

[0024] Alternatively, in the expansion molding step, the expansion temperature is 150-170°C.

[0025] The sarling resin in the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of the present invention, on the one hand, as a cationic polymer, can consume hydrogen fluoride, and can effectively reduce the yellowing phenomenon of polyvinylidene fluoride during processing and use, reduce the generation of conjugated structures in the polyvinylidene fluoride resin structure, and reduce the yellowing phenomenon of the product appearance; on the other hand, as a nucleating agent, it can improve the transparency and flexibility of the material, which is conducive to the wide application of polyvinylidene fluoride materials. Specific embodiments

[0026] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0027] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0029] Polyvinylidene fluoride resin is usually used to produce sheaths and main insulators for wire and cable products, especially heat shrink tubing. The following problems may occur during the preparation and use process: (1) The extrusion molding process requires high temperatures of 200 to 300°C; (2) The radiation cross-linking process requires high-energy electron beam radiation cross-linking modification; (3) During use, it is exposed to a high temperature (100 to 200°C) environment. These high temperatures and high-energy electron beams will cause the polyvinylidene fluoride molecular chain to undergo a dehalogenation reaction to generate hydrogen fluoride, accompanied by the formation of a conjugated double bond structure, causing the material color to turn yellow and dark, and its transparency to decrease.

[0030] Yellowing not only changes the appearance color of polyvinylidene fluoride products, but also reduces the transparency of the products, which cannot meet the needs of customers who have strict requirements on product appearance. In addition, the yellowing phenomenon is accompanied by a decrease in the toughness of the material. The deeper the yellowing, the more brittle the polyvinylidene fluoride pipe is. The embrittlement problem directly affects the performance and life of the product, bringing unfavorable and unstable factors to downstream customers. Therefore, developing a formula that can effectively improve the yellowing phenomenon of polyvinylidene fluoride materials has significant production benefit value, which can fundamentally improve the appearance of the product, ensure product identity, reduce the unqualified rate, and extend the service life of the product, thereby obtaining customer recognition and other benefits.

[0031] Based on this, the first aspect of the present invention provides a yellowing-resistant polyvinylidene fluoride heat shrinkable tube, and the yellowing-resistant polyvinylidene fluoride heat shrinkable tube preparation material includes the following raw materials in parts by weight:

[0032] 100 parts of polyvinylidene fluoride resin;

[0033] 2 to 10 parts of sarling resin.

[0034] The sarling resin in the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of the present invention, on the one hand, as a cationic polymer, can consume hydrogen fluoride, and can effectively reduce the yellowing phenomenon of polyvinylidene fluoride during processing and use, reduce the generation of conjugated structures in the polyvinylidene fluoride resin structure, and reduce the yellowing phenomenon of the product appearance; on the other hand, as a nucleating agent, it can improve the transparency and flexibility of the material, which is conducive to the wide application of polyvinylidene fluoride materials.

[0035] In some embodiments, the material for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube further includes the following raw materials in parts by weight: 0.5 to 3 parts of a NOR-type hindered amine stabilizer.

[0036] It is understandable that NOR hindered amine stabilizers can effectively inhibit and consume hydrogen fluoride. The introduction of alkoxy groups reduces the electron cloud density around active nitrogen atoms, participates in the cycle of capturing free radicals, maintains the stability of polymer materials, and can reduce the impact of yellowing. At the same time, the number of added parts is only 0.5-3 parts, which is relatively small, reducing the impact on the transparency of the heat shrinkable tube. Traditional hindered amine stabilizers have weak anti-yellowing effects and have high alkalinity. They are very easy to react with acidic substances to form salt precipitation, which will affect the transparency of the heat shrinkable tube. The number of NOR hindered amine stabilizers will affect the transparency of products made from polyvinylidene fluoride materials. If the number is too much, although the anti-yellowing effect is improved, the transparency of the product will decrease; if the number is too little, it will not have an anti-yellowing effect.

[0037] Preferably, the NOR type hindered amine stabilizer is a monomolecular N-alkoxy hindered amine stabilizer; preferably, the melting range is 108-123°C.

[0038] In some embodiments, the polyvinylidene fluoride is a copolymerized polyvinylidene fluoride.

[0039] In some embodiments, the copolymerized polyvinylidene fluoride has a melt index of 1 to 15 g / 10 min (230° C. / 5 kg) and a melt viscosity of 500 to 2500 Pa·s (230° C., 100 s -1 ).

[0040] Melt index (MI) is an important parameter to measure the fluidity of thermoplastics in a molten state. It uses a melt index tester to measure the mass of a material passing through a standard die capillary within a certain period of time (usually 10 minutes) under specified conditions. The unit is g / 10min. This parameter has important guiding significance for ensuring the quality of thermoplastics and their products and adjusting the production process. The larger the value of the melt index, the smaller the viscosity of the raw material, the smaller the molecular weight, the better the fluidity, and the better the processing performance; conversely, the smaller the value, the greater the viscosity of the raw material, the larger the molecular weight, the worse the fluidity, the worse the processing performance, but the higher the physical and mechanical properties.

[0041] Melt viscosity refers to the ability of a melt to resist the irreversible position change (flow) of its volume element. It is numerically the ratio of the shear stress of the melt to the shear rate, with the unit of Pa·s. For non-Newtonian fluids, the viscosity changes with the shear rate, and the resulting viscosity is called the apparent shear viscosity at the corresponding shear rate.

[0042] The melt index is 1-15 g / 10 min (230°C / 5 kg), and the melt viscosity is 500-2500 Pa·s (230°C, 100 s -1 ) copolymer PVDF has good processing performance, physical and mechanical properties and good transparency.

[0043] In some embodiments, the sarling resin is at least one of ethylene-(meth)acrylic acid zinc salt, sodium salt, and lithium salt ionomers.

[0044] As can be understood, Surlyn resin has extremely high transparency and is composed of ethylene-methacrylic acid copolymer (EMAA) partially coated with metal ions (Zn 2+ Or Na + or Li + ) is a thermoplastic resin containing covalent bonds made by neutralization. On the one hand, it can consume hydrogen fluoride as a cationic polymer, and on the other hand, it can improve the transparency and flexibility of the material as a nucleating agent.

[0045] In some embodiments, the material for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube further includes the following raw materials in parts by weight: 0.1 to 2 parts of a cross-linking sensitizer.

[0046] In some embodiments, the crosslinking sensitizer is at least one of trimethylallyl isocyanate and its derivatives, triallyl cyanurate and its derivatives, tripropargyl cyanurate and its derivatives, trimethylolpropane trimethacrylate and its derivatives, and trimethylolpropane triacrylate and its derivatives. The addition of the crosslinking sensitizer increases the number of active free radicals in the system, thereby reducing the energy of the electron beam originally required, thereby reducing the occurrence of dehalogenation reactions. In addition, even if a part of the dehalogenation reaction inevitably occurs, a sufficient amount of active free radicals can open the C=C double bond generated by the dehalogenation reaction again, while promoting the required crosslinking reaction, consuming the conjugated double bonds. Under the action of sarin resin or NOR-type hindered amine stabilizer, it is further guaranteed that the PVDF resin will not turn yellow during the processing process, and the product can maintain its original color.

[0047] In a second aspect of the present invention, there is provided a method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube, which comprises the following steps:

[0048] Masterbatch processing: polyvinylidene fluoride resin and surin resin are mixed evenly, extruded, drawn and pelletized by extrusion equipment to obtain masterbatch particles;

[0049] Extrusion into pipe: Extruding the masterbatch particles obtained above into pipes through an extrusion device to obtain semi-finished pipes;

[0050] Irradiation process: irradiate the semi-finished pipes through irradiation equipment, control the irradiation dose to 5-15 Mrad, and obtain irradiated pipes;

[0051] Expansion molding: the irradiated tube is expanded, cooled, and formed to obtain a yellowing-resistant polyvinylidene fluoride heat shrinkable tube.

[0052] It can be understood that the masterbatch processing: polyvinylidene fluoride resin and surin resin can be added to the internal mixer according to the ratio, the material temperature is controlled at 170±10°C, and the mixture is mixed for 8-15 minutes to obtain a mixture, and then the mixture is passed through an extrusion device, such as a twin-screw extruder or a single-screw extruder, extruded, stretched, and pelletized to obtain masterbatch particles;

[0053] Extrusion into tubes: The masterbatch particles after granulation are passed through an extruder, such as a single-screw extruder or a twin-screw extruder, to extrude tubes to obtain semi-finished tubes;

[0054] Irradiation process: The semi-finished pipes are passed through irradiation equipment, such as electron accelerator irradiation device or radioactive isotope irradiation device, and the irradiation dose is controlled to be 5-15 Mrad to obtain irradiated pipes; by adding sarin resin, even if the irradiation dose during the irradiation process is slightly higher, yellowing will not occur.

[0055] Expansion molding: the irradiated tube is expanded, cooled, and formed to obtain a yellowing-resistant polyvinylidene fluoride heat shrinkable tube.

[0056] In some embodiments, in the masterbatch processing step, when the polyvinylidene fluoride resin and the surin resin are mixed, at least one of a NOR-type hindered amine stabilizer and a cross-linking sensitizer is also added and mixed.

[0057] In some embodiments, in the extrusion tube step, the extrusion temperature of the extrusion equipment is 180-250° C. It can be understood that the extrusion temperature of the extrusion equipment is 180-250° C., which can not only ensure that the tube can be melt-extruded and has a smooth surface, but also reduce the occurrence of yellowing.

[0058] In some embodiments, in the extrusion tube step, the stretch ratio of the extruded tube is controlled to be 8-40, which can improve the transparency of the polyvinylidene fluoride heat shrinkable tube.

[0059] It is understandable that in the extrusion tube step, the die and the mandrel are generally selected according to the size requirements, and the pulling speed and the extrusion speed are controlled to obtain tubes with different stretch ratios. The stretch ratio of the extruded tube is related to the transparency of the polyvinylidene fluoride heat shrinkable tube. If the stretch ratio is too low, the transparency of the polyvinylidene fluoride heat shrinkable tube will deteriorate. If the stretch ratio is too high, the mechanical properties of the polyvinylidene fluoride heat shrinkable tube will decrease. Furthermore, 0.5-3 parts of NOR type hindered amine stabilizer and the stretch ratio in the range of 8-40 have a synergistic effect, which can further improve the transparency and mechanical properties of the heat shrinkable tube.

[0060] In some embodiments, in the expansion molding step, the expansion temperature is 150-170°C.

[0061] The present invention is further described in detail below with reference to specific embodiments.

[0062] Determination of stretch ratio

[0063] A single screw extruder is used, and the specifications of the extrusion die are as follows: the die is D1 (mm), the core rod is D2 (mm), and the size of the extruded pipe is as follows: the inner diameter of the extruded pipe is d1 (mm), and the wall thickness is w (mm) (depending on the size of the extruded pipe, the corresponding model of extruder, die and core rod must be selected). During the extrusion process, we control the traction speed and extrusion speed to obtain pipes with different stretch ratios. The stretch ratio calculation formula is as follows:

[0064]

[0065] The yellowing-resistant polyvinylidene fluoride heat shrinkable tubing of the present invention is described in the following examples and comparative examples.

[0066] Example 1

[0067] Please refer to Table 1. The raw materials for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment include the following raw materials in parts by weight:

[0068] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0069] 2 parts of Surlyn resin (DuPont, 8940).

[0070] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube is as follows:

[0071] Masterbatch processing: Add polyvinylidene fluoride resin and surin resin into an internal mixer according to the proportion, control the material temperature at 170±10℃, mix for 8-15min to obtain a mixture; then crush the mixture, extrude, draw, and air-cool pelletize at a temperature of 160-220℃ to obtain masterbatch particles;

[0072] Extrusion into tube: The masterbatch particles obtained above are extruded by a single screw extruder at an extrusion temperature of 180-250° C., and the extrusion tube stretching ratio is controlled to be 5 to obtain a semi-finished sleeve;

[0073] Irradiation process: the semi-finished casing is irradiated by an electron accelerator device, the irradiation dose is controlled to be 8 Mrad, and irradiation cross-linking is performed to obtain an irradiated pipe;

[0074] Expansion molding: The irradiated tube is expanded twice by using an expansion device at 150-170°C; then cooled and shaped to obtain a finished heat shrink tube.

[0075] Example 2

[0076] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Embodiment 1, see Table 1.

[0077] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 1, except that in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 50, see Table 1.

[0078] Example 3

[0079] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 1, except for the number of components, as shown in Table 1:

[0080] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0081] 6 parts of Surlyn resin (DuPont, 8940).

[0082] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 1, except that in the masterbatch processing step, the components and proportions of each raw material are different, see Table 1.

[0083] Example 4

[0084] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 1, except for the number of components, as shown in Table 1:

[0085] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0086] 6 parts of Surlyn resin (DuPont, 8940).

[0087] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 1, except that in the masterbatch processing step, the components and proportions of each raw material are different; in the extrusion tube step, the stretch ratio of the extruded tube is controlled to be 50, please see Table 1.

[0088] Example 5

[0089] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 1, except that the composition and number of each component are shown in Table 1:

[0090] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0091] 10 parts of Surlyn resin (DuPont, 8940).

[0092] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 1, except that in the masterbatch processing step, the components and proportions of each raw material are different, see Table 1.

[0093] Example 6

[0094] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 1, except that the composition and number of each component are shown in Table 1:

[0095] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0096] 10 parts of Surlyn resin (DuPont, 8940).

[0097] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 1, except that in the masterbatch processing step, the components and proportions of each raw material are different; in the extrusion tube step, the stretch ratio of the extruded tube is controlled to be 50, please see Table 1.

[0098] Example 7

[0099] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 3, except that the composition and number of each component are shown in Table 1:

[0100] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0101] 6 parts of Surlyn resin (DuPont, 8940);

[0102] NOR type hindered amine stabilizer: (BASF, NOR116) 0.5 parts.

[0103] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 3, except that in the masterbatch processing step, the components and proportions of each raw material are different, see Table 1.

[0104] Example 8

[0105] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 3, except that the composition and number of each component are shown in Table 1:

[0106] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0107] 6 parts of Surlyn resin (DuPont, 8940);

[0108] NOR type hindered amine stabilizer: (BASF, NOR116) 0.5 parts.

[0109] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 3, except that in the masterbatch processing step, the components and proportions of each raw material are different; in the extrusion tube step, the stretch ratio of the extruded tube is controlled to be 50, please refer to Table 1.

[0110] Example 9

[0111] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 3, except that the composition and number of each component are shown in Table 1:

[0112] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0113] 6 parts of Surlyn resin (DuPont, 8940);

[0114] NOR type hindered amine stabilizer: (BASF, NOR116) 1.8 parts.

[0115] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 3, except that in the masterbatch processing step, the components and proportions of each raw material are different, see Table 1.

[0116] Example 10

[0117] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 3, except that the composition and number of each component are shown in Table 1:

[0118] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0119] 6 parts of Surlyn resin (DuPont, 8940);

[0120] NOR type hindered amine stabilizer: (BASF, NOR116) 3 parts.

[0121] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 1, except that in the masterbatch processing step, the components and proportions of each raw material are different, see Table 1.

[0122] Embodiment 11

[0123] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 3, except that the composition and number of each component are shown in Table 1:

[0124] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0125] 6 parts of Surlyn resin (DuPont, 8940);

[0126] NOR type hindered amine stabilizer: (BASF, NOR116) 3 parts.

[0127] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 1, except that in the masterbatch processing step, the components and proportions of each raw material are different; in the extrusion tube step, the stretch ratio of the extruded tube is controlled to be 50, please see Table 1.

[0128] Example 12

[0129] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Embodiment 3, see Table 1.

[0130] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 3, except that in the irradiation process step, the irradiation dose is changed to 5 Mrad, see Table 1.

[0131] Embodiment 13

[0132] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Embodiment 3, see Table 1.

[0133] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 3, except that in the irradiation process step, the irradiation dose is changed to 12 Mrad, see Table 1.

[0134] Embodiment 14

[0135] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Embodiment 3, see Table 1.

[0136] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 3, except that in the irradiation process step, the irradiation dose is changed to 15 Mrad, see Table 1.

[0137] Embodiment 15

[0138] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Embodiment 3, see Table 1.

[0139] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 3, except that in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 8, see Table 1.

[0140] Example 16

[0141] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Embodiment 3, see Table 1.

[0142] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 3, except that in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 24, see Table 1.

[0143] Embodiment 17

[0144] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Embodiment 3, see Table 1.

[0145] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Embodiment 3, except that in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 40, see Table 1.

[0146] Embodiment 18

[0147] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Example 7, please refer to Table 1.

[0148] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 7, except that in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 8, see Table 1.

[0149] Embodiment 19

[0150] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Example 10, please refer to Table 1.

[0151] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 10, except that in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 8, see Table 1.

[0152] Embodiment 20

[0153] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Example 7, please refer to Table 1.

[0154] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 7, except that in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 40, see Table 1.

[0155] Embodiment 21

[0156] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is the same as that of Example 11, please see Table 1.

[0157] The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this embodiment is basically the same as that of Example 11, except that in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 40, please refer to Table 1.

[0158] Comparative Example 1

[0159] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except for the number of components, as shown in Table 1:

[0160] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20).

[0161] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that in the masterbatch processing step, the component parts of each raw material are different, please refer to Table 1.

[0162] Comparative Example 2

[0163] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except for the number of components, as shown in Table 1:

[0164] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0165] 1 part of Surlyn resin (DuPont, 8940).

[0166] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that in the masterbatch processing step, the component parts of each raw material are different, please refer to Table 1.

[0167] Comparative Example 3

[0168] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except for the number of components, as shown in Table 1:

[0169] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0170] 12 parts of Surlyn resin (DuPont, 8940).

[0171] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that in the masterbatch processing step, the component parts of each raw material are different, please refer to Table 1.

[0172] Comparative Example 4

[0173] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except for the composition and quantity of each raw material, as shown in Table 1:

[0174] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0175] 6 parts of Surlyn resin (DuPont, 8940);

[0176] NOR type hindered amine stabilizer: (BASF, NOR116) 0.3 parts.

[0177] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that the composition and quantity of each raw material in the masterbatch processing step are different, please refer to Table 1.

[0178] Comparative Example 5

[0179] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except for the composition and quantity of each raw material, as shown in Table 1:

[0180] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0181] 6 parts of Surlyn resin (DuPont, 8940);

[0182] NOR type hindered amine stabilizer: (BASF, NOR116) 4 parts.

[0183] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that the composition and quantity of each raw material in the masterbatch processing step are different, please refer to Table 1.

[0184] Comparative Example 6

[0185] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except for the composition and quantity of each raw material, as shown in Table 1:

[0186] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0187] 6 parts of Surlyn resin (DuPont, 8940);

[0188] Hindered amine stabilizer (BASF, 944) 3 parts.

[0189] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that the composition and quantity of each raw material in the masterbatch processing step are different, please refer to Table 1.

[0190] Comparative Example 7

[0191] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is the same as that of Example 3, please refer to Table 1.

[0192] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that in the irradiation process step, the irradiation dose is changed to 3 Mrad, see Table 1.

[0193] Comparative Example 8

[0194] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is the same as that of Example 3, please refer to Table 1.

[0195] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that in the irradiation process step, the irradiation dose is changed to 17 Mrad, see Table 1.

[0196] Comparative Example 9

[0197] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except for the composition and quantity of each raw material, as shown in Table 1:

[0198] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0199] 6 parts of Surlyn resin (DuPont, 8940);

[0200] NOR type hindered amine stabilizer: (BASF, NOR116) 0.3 parts.

[0201] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that in the masterbatch processing step, the composition and quantity of each raw material are different; in the extrusion tube step, the stretch ratio of the extruded tube is controlled to be 50, please refer to Table 1.

[0202] Comparative Example 10

[0203] The raw material formula for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except for the composition and quantity of each raw material, as shown in Table 1:

[0204] 100 parts of polyvinylidene fluoride resin (Arkema, 2800-20);

[0205] 6 parts of Surlyn resin (DuPont, 8940);

[0206] NOR type hindered amine stabilizer: (BASF, NOR116) 4 parts.

[0207] The preparation method of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube of this comparative example is basically the same as that of Example 3, except that in the masterbatch processing step, the composition and quantity of each raw material are different; in the extrusion tube step, the stretch ratio of the extruded tube is controlled to be 50, please refer to Table 1.

[0208] The yellowing index, light transmittance and elongation at break of the finished product were measured. The results of the embodiments and comparative examples are shown in Table 2. The measurement method is as follows:

[0209] Determination of yellowing index

[0210] Use the Color Spectrum CS-820N spectrophotometer to measure the three stimulus values ​​X, Y, and Z of the material color under the standard C light source. The yellowing index YI=100(1.28X-1.06Z) / Y is calculated by the following formula. Generally, the material can be used normally if the yellowing index is lower than 2.0.

[0211] Determination of light transmittance

[0212] Use a Triumph YH600 haze meter to read the incident light flux T1 and the total transmitted light flux T2 passing through the sample, and calculate the transmittance Tt=T2 / 21×100% according to the following formula. Generally, a transmittance higher than 85% has better transparency.

[0213] Determination of elongation at break

[0214] The high-speed rail AI-7000-SU1 tensile testing machine is used to measure the length L0 before stretching and the length L when stretched to fracture. The elongation at break is calculated by the following formula ε=(L-L0) / L0×100%. Generally, the mechanical properties are better when the elongation at break is higher than 400%.

[0215] Table 1 Composition and mass fraction of each raw material of yellowing-resistant polyvinylidene fluoride heat shrinkable tube in the embodiment and comparative example, preparation process parameters

[0216]

[0217]

[0218]

[0219] Table 2 Test results of yellowing-resistant polyvinylidene fluoride heat shrink tubing obtained in Examples and Comparative Examples

[0220]

[0221]

[0222] As shown in Table 2, the yellowing index of the yellowing-resistant polyvinylidene fluoride heat shrinkable tube prepared in Example 1 to Example 21 is lower than 2.0, and the yellowing-resistant effect is good. Although the yellowing-resistant polyvinylidene fluoride heat shrinkable tube prepared in Example 1, 3, and 5 has a good yellowing-resistant effect, the light transmittance is between 82% and 85%, which still needs to be improved; although the yellowing-resistant polyvinylidene fluoride heat shrinkable tube prepared in Example 2, 4, and 6 has a good yellowing-resistant effect, the elongation at break is between 350% and 370%, and the mechanical properties need to be improved; the yellowing-resistant polyvinylidene fluoride heat shrinkable tube prepared in Example 12, 13, and 14 has a good yellowing-resistant effect. In a relatively wide range of irradiation doses, the yellowing index is lower than 2.0, and the yellowing-resistant effect is good. However, as the irradiation dose continues to increase, although the heat shrinkable tube still has a good yellowing-resistant effect, it has a certain impact on the subsequent expansion process, which in turn affects the mechanical properties related to the heat shrinkable tube, causing the mechanical properties to decrease to a certain extent. Compared with Example 3, the yellowing-resistant polyvinylidene fluoride heat shrink tubing prepared in Examples 7, 9, and 10 has good yellowing resistance and improved transparency by adding a certain amount of NOR hindered amine stabilizer. Compared with Comparative Examples 4, 5, 9, and 10, the yellowing-resistant polyvinylidene fluoride heat shrink tubing prepared in Examples 7, 10, 8, and 11 has good yellowing resistance and improved transparency by controlling the NOR hindered amine stabilizer in the range of 0.5-3 parts without controlling the stretch ratio range; Compared with Examples 3 and 4, the yellowing-resistant polyvinylidene fluoride heat shrink tubing prepared in Examples 15-17 has good yellowing resistance and improved transparency and mechanical properties by controlling the stretch ratio in the range of 8-40 without adding NOR hindered amine stabilizer; Compared with Examples 7 and 8, the yellowing-resistant polyvinylidene fluoride heat shrink tubing prepared in Examples 18 and 20 has good yellowing resistance and improved transparency and mechanical properties by adding 0.5 parts of NO Under the condition of R-type hindered amine stabilizer, by controlling the stretch ratio within the range of 8-40, not only the yellowing resistance effect is good, but also the transmittance and elongation at break are higher, and the transparency and mechanical properties are more excellent; the yellowing-resistant polyvinylidene fluoride heat shrinkable tubes prepared in Examples 19 and 21 are compared with the corresponding Examples 10 and 11. Under the condition of adding 3 parts of NOR-type hindered amine stabilizer, by controlling the stretch ratio within the range of 8-40, not only the yellowing resistance effect is good, but also the transmittance and elongation at break are higher, and the transparency and mechanical properties are more excellent; it can be seen that 0.5-3 parts of NOR-type hindered amine stabilizer and the stretch ratio within the range of 8-40 have a synergistic effect, which can further improve the yellowing resistance, transparency and mechanical properties of the heat shrinkable tube.

[0223] In Comparative Example 1, no sarling resin was added, and the heat shrink tube turned yellow seriously, and the transparency and mechanical properties were seriously reduced;

[0224] Comparative Example 2: The amount of sarling resin is too low, the heat shrink tube turns yellow seriously, and the transparency and mechanical properties decrease;

[0225] In Comparative Example 3, the proportion of sarling resin is too high, which helps to improve the yellowing phenomenon of the heat shrink tube, but affects the transparency and mechanical properties.

[0226] In Comparative Example 4, the amount of NOR hindered amine stabilizer is too low, the draw ratio of the extruded tube is too low, and the yellowing resistance and transparency of the heat shrinkable tube are not significantly improved;

[0227] Comparative Example 5: The amount of NOR hindered amine stabilizer is too high, the draw ratio of the extruded tube is too low, the yellowing resistance of the heat shrinkable tube is improved, but the transparency is affected;

[0228] Comparative Example 6 uses other types of hindered amine stabilizers, and the heat shrinkable tube has poor yellowing resistance and low transparency;

[0229] The irradiation dose of Comparative Example 7 is too low, and the mechanical properties of the heat shrink tube are low;

[0230] In Comparative Example 8, the irradiation dose was too high, the heat shrink tube turned yellow seriously, and the transparency was seriously reduced;

[0231] Comparative Example 9: The amount of NOR hindered amine stabilizer is too low, the draw ratio of the extruded tube is too high, and the heat shrink tube has low transparency and low mechanical properties;

[0232] In Comparative Example 10, the proportion of NOR hindered amine stabilizer is too high, and the draw ratio of the extruded tube is too high. Although the yellowing resistance of the heat shrinkable tube can be improved, the transparency is reduced and the mechanical properties are low.

[0233] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A yellowing-resistant polyvinylidene fluoride heat shrinkable tube, characterized in that: The material for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube comprises the following raw materials in parts by weight: 100 parts of polyvinylidene fluoride resin; 2 to 10 parts of sarling resin.

2. The yellowing-resistant polyvinylidene fluoride heat shrinkable tube according to claim 1, characterized in that: The following ingredients are also included: 0.5 to 3 parts of NOR type hindered amine stabilizer.

3. The yellowing-resistant polyvinylidene fluoride heat shrinkable tube according to claim 2, characterized in that: The NOR type hindered amine stabilizer is a single molecule N-alkoxy hindered amine stabilizer with a melting range of 108-123°C.

4. The yellowing-resistant polyvinylidene fluoride heat shrinkable tube according to claim 1, characterized in that: The polyvinylidene fluoride is copolymerized polyvinylidene fluoride.

5. The yellowing-resistant polyvinylidene fluoride heat shrinkable tube according to claim 4, characterized in that: The copolymerized polyvinylidene fluoride has a melt index of 1 to 15 g / 10 min (230° C. / 5 kg) and a melt viscosity of 500 to 2500 Pa·s (230° C., 100 s -1 ).

6. The yellowing-resistant polyvinylidene fluoride heat shrinkable tube according to claim 1, characterized in that: The sarling resin is at least one of ethylene-(meth)acrylic acid zinc salt, sodium salt, and lithium salt ion bond polymers.

7. The yellowing-resistant polyvinylidene fluoride heat shrinkable tube according to claim 1, characterized in that: The following ingredients are also included: Cross-linking sensitizer 0.1 to 2 parts.

8. The yellowing-resistant polyvinylidene fluoride heat shrinkable tube according to claim 7, characterized in that: The cross-linking sensitizer is at least one of trimethallyl isocyanate and its derivatives, triallyl cyanurate and its derivatives, tripropargyl cyanurate and its derivatives, trimethylolpropane trimethacrylate and its derivatives, and trimethylolpropane triacrylate and its derivatives.

9. A method for preparing a yellowing-resistant polyvinylidene fluoride heat shrinkable tube, characterized in that: The following steps are involved: Masterbatch processing: polyvinylidene fluoride resin and surin resin are mixed evenly, extruded, drawn and pelletized by extrusion equipment to obtain masterbatch particles; Extrusion into pipe: Extruding the masterbatch particles obtained above into pipes through an extrusion device to obtain semi-finished pipes; Irradiation process: irradiate the semi-finished pipes through irradiation equipment, control the irradiation dose to 5-15 Mrad, and obtain irradiated pipes; Expansion molding: the irradiated tube is expanded, cooled, and formed to obtain a yellowing-resistant polyvinylidene fluoride heat shrinkable tube.

10. The method for preparing the yellowing-resistant polyvinylidene fluoride heat shrinkable tube according to claim 9, characterized in that: In the masterbatch processing step, when the polyvinylidene fluoride resin and the surin resin are mixed, at least one of a NOR type hindered amine stabilizer and a cross-linking sensitizer is also added for mixing; Or, in the extrusion tube forming step, the extrusion temperature of the extrusion equipment is 180-250°C; Or, in the extrusion tube forming step, the stretching ratio of the extruded tube is controlled to be 8-40; Alternatively, in the expansion molding step, the expansion temperature is 150-170°C.

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