KR20110048339A - Highly flame-retardant, halogen-free colored heat-shrink tubing - Google Patents

Abstract

PURPOSE: A heat-shrink tube composition is provided to avoid halogen, to ensure excellent mechanical properties and high fire retardant characteristic while improving colorability. CONSTITUTION: A heat-shrink tube composition includes, 100 parts by weight of an ethylene-vinyl acetate copolymer base resin; 30-100 parts by weight of a phosphorous-based flame retardant except for red phosphors; and 5-15 parts by weight of silicon-based flame retardant aid. The base resin includes the ethylene-vinyl acetate copolymer with a melting index of 2-15 g/10 minute, polymerized with 15-33% of vinyl acetate monomer. The phosphorous-based flame retardant is ammonium polyphosphate represented by chemical formula 1.

Description

High flame retardant non-halogen colored heat shrink tube {HIGHLY FLAME-RETARDANT, HALOGEN-FREE COLORED HEAT-SHRINK TUBING}

The present invention relates to a heat shrink tube and a resin composition therefor. More specifically, it is a non-halogen high flame-retardant heat shrink tube, Comprising: It is related with the resin composition for heat-shrink tubes which matched mechanical properties and flame retardance, and its heat-shrink tube.

The heat shrink tube is a tube having a property of shrinking in diameter or length when heated, and is also used for packaging by tightly covering a connection part such as a coated wire or a pipe or being inserted into an outer circumferential surface of a bottle or a battery. In a widely used method of manufacturing a heat shrink tube, the thermoplastic resin is first extruded, and then the thermoplastic resin is crosslinked using a method such as electron beam irradiation. The crosslinked resin is then heated to a temperature above its crystal melting temperature to expand and then cooled to prepare the final product. In such a heat shrink tube, a product or part to be coated or packaged is inserted into a hollow portion inside the heat shrink tube and stayed at an appropriate temperature so that the heat shrink tube is contracted to be in close contact with the product or part therein.

Conventional heat shrink tubes are not suitable for use in environment-friendly high flame-retardant heat shrink tube because the use of polyvinyl chloride (PVC) material, bromine-based flame retardant, antimony-based flame retardant. PVC is characterized by excellent water resistance, chemical resistance, flame retardancy, etc., but incomplete combustion generates dioxin, a mutagen suspected to be a carcinogen. Therefore, the recent trend is regulating the use of PVC. Halogen-based flame retardants, including bromine-based, have the advantage of exhibiting high flame retardancy in a small amount, but they cause environmental problems, and their use is restricted due to safety such as generation of toxic gases during combustion.

Thus, efforts have been made to use inorganic flame retardants to replace halogen flame retardants. Among them, the metal hydroxide flame retardant has attracted attention because of its environmental friendliness, but since excessive amounts of flame retardancy required by industrial standards can be reached, mixing a large amount of an inorganic compound with a heterogeneous polymer resin degrades the mechanical properties of the composition. There was. This is because metal hydroxides with very high polarity do not disperse well in the polymer resin, but rather are bound together. Metal hydroxide flame retardants also have the problem of not only bringing down the properties due to hydrolysis at high temperatures but also making the expansion process, which is one of the manufacturing processes of the heat shrink tube, in severe cases impossible. In the case of a heat shrink tube, an expansion process is necessarily included, unlike a general wire manufacturing process. In particular, a heat shrink tube has a larger amount of heat to be applied in the expansion process than a non-thick heat shrink tube to support the expansion process. The importance of flame retardant compositions that can be made is even more urgent. For this reason, the large diameter heat shrinkable tube containing a non-halogen inorganic flame retardant in 150 weight part or more is very difficult to manufacture by a conventional technique.

Attempts have been made to use red phosphorus as a non-halogen inorganic flame retardant rather than as a metal hydroxide. Red phosphorus has excellent flame retardancy compared to metal hydroxides, but it has a reddish brown color, which deteriorates the appearance of the finished tube and makes it almost impossible to implement various colors.

Therefore, as a composition for non-halogen-type heat-shrinkable tubes having sufficient flame retardancy, the demand for a composition for heat-shrinkable tubes having excellent harmony of mechanical properties and flame retardancy and capable of realizing various colors desired is still not sufficiently responsive in the industry.

The technical problem of the present invention is to develop a resin composition for a high flame retardant heat shrinkable tube having mechanical properties, flame retardancy and colorability as a polymer resin composition for a highly flame retardant heat shrinkable tube containing no halogen component.

In order to achieve the above object, the resin composition for heat shrinkable tube of the present invention is 30 to 100 parts by weight of phosphorus-based flame retardant excluding red phosphorus and 5 to 15 parts of silicone-based auxiliary flame retardant based on 100 parts by weight of the base resin made of ethylene-vinyl acetate copolymer. It includes parts by weight. In this case, the base resin is characterized in that the melt index is an ethylene-vinyl acetate copolymer having a melt index of 2 g / 10 min to 15 g / 10 min, polymerized by setting the proportion of the vinyl acetate monomer to 15 to 33% by weight.

As the phosphorus flame retardant of the resin composition for a heat shrinkable tube of the present invention, ammonium polyphosphate represented by the following general formula (1) is preferable, and n in the general formula (1) is preferably 1000 ≦ n ≦ 2000 as an integer.

The ammonium polyphosphate is more preferably ammonium polyphosphate coated with melamine formaldeide.

The present invention also provides a heat shrink tube manufactured using the resin composition for heat shrink tubes.

The heat shrink tube manufactured using the resin composition for heat shrink tube of the present invention can implement excellent mechanical properties and high flame retardancy according to the UL 224 standard, and can exhibit various colors due to excellent colorability.

Hereinafter, the present invention will be described in detail. The flame-retardant resin composition for heat shrinkable tubes of the present invention is characterized by using a phosphorus-based flame retardant and a silicone-based auxiliary flame retardant together except red phosphorus in a basic resin which is an ethylene-vinyl acetate copolymer.

Phosphorus-based flame retardant in the present invention uses 30 to 100 parts by weight based on 100 parts by weight of the base resin. Phosphorous main flame retardants of the present invention include phosphate ester, 3-hydroxyphenylphosphinyl propanoic acid, tricresyl phosphate, ammonium phosphate, ammonium poly phosphate, melamine phosphate, dimelamine phosphate, triethylene phosphate, ammonium polyphosphate ( ammonium polyphosphate (APP) and the like can be used, especially ammonium polyphosphate (APP) is suitable. Ammonium polyphosphate, a colorless flame retardant, is an organic material and is advantageous for expansion processes because its elongation rate does not decrease as much as metal hydroxide. Ammonium polyphosphate decomposes when exposed to fire or heat, splitting into polyphosphoric acid and ammonia. Polyphosphoric acid acts on the surrounding hydroxyl groups to form unstable phosphate esters and dehydrates again to form a carbon foam layer near the fire source. Dilatation effect-intumescence). This foam acts as a barrier to reduce fire damage, a phenomenon called carbonaceous char or simply char formation. In other words, ammonium polyphosphate has an advantage in that mechanical degradation is less than that of a metal hydroxide flame retardant and the formation of tea is excellent in terms of flame retardant effect.

However, ammonium polyphosphate, like red phosphorus, does not disperse well in polymer resins, and using large amounts can deteriorate the appearance of the heat shrink tube, and less than metal hydroxides, but can also reduce mechanical strength. Flame retardant resin composition using ammonium polyphosphate has excellent disadvantages of self-extinguishing, but drips, ie, plastics, are vulnerable to melting due to high heat, resulting in a phenomenon in which fire falls off and transfers.

In the present invention, in order to compensate for these disadvantages of ammonium polyphosphate, on the one hand, by using a colorless silicone-based auxiliary flame retardant, it exhibits high flame retardancy even without excess polyammonium phosphate, and achieves even dispersion to prevent mechanical property deterioration, and various colors. To be able to implement

In a preferred embodiment of the present invention, ammonium polyphosphate of Formula 1 is used as a phosphorus flame retardant, and ammonium polyphosphate may be classified according to the number (n) of phosphates.

[Formula 1]

In the present invention, ammonium polyphosphate (Crystal phase II) having from 1000 to 2,000 phosphates is used. If ammonium polyphosphate (Crystal phase I) having less than 1000 phosphates is used, the water stability is increased so that hydrolysis occurs a lot so that the thermal stability of the resin composition for the heat shrinkable tube is reduced. do.

In addition, in the present invention, when the ammonium polyphosphate coated with melamine formaldeide is used, heat sensitivity of the heat-reducing tube resin composition may be reduced since the moisture sensitivity may be reduced compared to the case of using the ammonium polyphosphate without the melamine formaldehyde coated. Stability can be improved.

In the present invention, the silicone-based auxiliary flame retardant increases the flame retardancy by preventing drips, and serves to reduce the amount of the main flame retardant. Silicone-based flame retardants have low hazards and relatively high flame retardancy and good dispersibility in polymer resins. The silicon-based flame retardant can be said to have a flame retardant effect by forming a composite inorganic layer of a white combustion residue having a -Si-O- bond and a -Si-C- bond and a carbonized carbide.

The base resin of the composition according to the invention is a copolymer of ethylene-vinyl acetate (EVA). Crystalline resins such as polyethylene (PE), which is one of ethylene-based copolymers, have a disadvantage of poor flame retardancy and poor drip characteristics. EVA copolymer resin has the same flexibility and rubber elasticity as soft PVC, has excellent molding processability, resists cracking by stress, and is hygienic and non-toxic. Since the EVA resin can adjust the physical properties according to the content of vinyl acetate (VA), when used as a material of the heat shrink tube, flexibility and strength can be appropriately harmonized. Since the EVA resin is more compatible with polyethylene than the phosphorus-based flame retardant of the present invention, it helps to evenly disperse the flame retardant and prevents mechanical property degradation caused by the flame retardant.

As the ethylene-vinyl acetate copolymer, a single ethylene-vinyl acetate copolymer or a mixture of these copolymers polymerized such that the weight of the vinyl acetate monomer accounts for 15 to 33% of the total monomer weight of ethylene and vinyl acetate is used. do. Since the ethylene-vinyl acetate copolymer resin has a low melting point and a relatively high content of vinyl acetate, the flexibility is large, and thus the tensile modulus at high temperature can be kept small. When using an EVA resin polymerized with a vinyl acetate monomer content less than 15% by weight, the modulus becomes large due to lack of flexibility, and when using an EVA resin of more than 33% by weight, the strength is insufficient to satisfy the specification of the heat shrink tube. You won't be able to.

And as the EVA resin, it is preferable to use a copolymer having a melt flow index of 2 g / 10 minutes to 15 g / 10 minutes. Heat shrink tubes made of EVA resin with a melt index of less than 2 have the disadvantage of increasing the high temperature modulus due to poor flow of resin, and heat shrink tubes having a melt index of more than 15 g / 10 minutes have high flowability, so that extrusion molding is difficult. It is not preferable because there is a problem that it is impossible.

The composition for producing a flame-retardant heat-shrink tube according to the present invention may include any one material selected from an antioxidant, a crosslinking aid, and a lubricant, or two or more materials. Antioxidants protect physical properties by preventing air oxidation of polymer resins that occur at high temperatures. As the antioxidant of the present invention, it is preferable to use a single substance selected from a group of thioester-based and phenolic substances or a mixture of two or more selected from them, and A / O 1010 is suitable as a specific example. In the present invention, the antioxidant is included in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the base resin.

As the crosslinking aid of the present invention, it is preferable to use a trimethacrylate-based material. As a specific trimethacrylic acid-based material, trimethylol trimethacrylate is preferable. In the present invention, the crosslinking aid is included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the base resin. In the case of below the lower limit, the effect of the addition of the crosslinking aid is insignificant, and in the case of exceeding the upper limit, the initial crosslinking reaction rate is rapidly increased, thereby increasing the crosslinking degree to produce a heat shrinkable tube. The problem arises that the expansion process, which is part of the process, becomes impossible.

In the present invention, it is possible to increase the release property from the metal surface and suppress the generation of frictional heat during the production of the heat shrinkable tube by using a lubricant. There are no particular limitations on the lubricants that can be used in the resin composition of the present invention, and any lubricants commonly used in the art may be used. Some examples include stearic acid, stearyl alcohol, butyl stearate, waxes, and the like. If the lubricant content is less than 0.5 parts by weight, there is no lubricating effect, and if it exceeds 10 parts by weight, the physical properties of the entire resin composition may be impaired, such as kneading becomes difficult, which is not preferable.

In addition, the composition for producing a heat shrinkable tube according to the present invention may further include various functional additives commonly used in the resin composition within a range that does not impair the effects of the present invention. Such additives include sunscreens, heat stabilizers, lubricants, antiblocking agents, antistatic agents, waxes, coupling agents, pigments, and the like, although not illustrated, various kinds of materials may be selected and used as necessary.

In this invention, the heat shrink tube manufactured using the said resin composition for heat shrink tubes is also provided. 1 is a cross-sectional view of a heat shrink tube for explaining an embodiment according to the present invention. 1 is a view to put the insert in a heat shrink tube having an empty space therein to shrink the tube to wrap the insert in close contact. The resin composition of the present invention can be used to prepare heat shrink tubes in various forms according to well known heat shrink tube manufacturing methods. That is, the resin composition of the present invention is extruded to produce a pipe having a desired diameter size, and the pipe is chemically treated or crosslinked using an electron beam or the like. The crosslinked pipe is heated to a temperature above the crystal melting temperature, and then the expanded heated pipe is expanded by the shrinkage of the resin measured in advance. In addition, the expanded pipe is cooled and cut to size to obtain various heat shrink tubes.

When the resin composition for flame retardant heat shrink tube according to the present invention is used, the high-temperature tensile modulus is low, so that the expansion process is easy, and the flame retardancy is good, it is useful for non-halogen heat shrink tube, and there is an advantage of making the heat shrink tube with improved colorability. .

The present invention will be described in more detail with reference to the following Examples. The average person skilled in the art to which the present invention pertains may change the present invention in various other forms in addition to the embodiments described in the following examples, and the following examples merely illustrate the present invention, and the scope of the technical spirit of the present invention is given below. It is not to be construed as limiting the scope of the examples.

In order to examine the performance change according to the composition of the resin composition for heat shrinkable tube of the present invention, the flame retardant resin compositions of Comparative Examples and Examples were prepared with the compositions shown in Table 1 below. All units in Table 1 are parts by weight, and component values deviating from the composition of the resin composition for a heat shrinkable tube according to the present invention are shown in bold italics.

Composition (parts by weight) Example Comparative Example One 2 3 One 2 3 4 5 EVA resin 1 (VA 25% by weight) ^* 100 100 100 100 80 100 100 100 EVA Resin 2 (VA 45 wt%) ^** ― ― ― ― 20 ―  Ammonium Polyphosphate Flame Retardant II 40 95 40 110 40 40 0 Ammonium Polyphosphate Flame RetardantⅠ 40 Silane-treated Mg (OH) ₂ flame retardant ― ― ― ― ― ― 200  Silicone auxiliary flame retardant 5 5 10 5 5 2 0 5

[Description of Components Used in Table]

* If the melt index of EVA resin 1 from Mitsui-dupont is 2.5 g / 10 min, vinyl acetate monomer accounts for 25% by weight of the mixture of monomers.

** If the melt index of EVA resin 2 from Mitsui-dupont is 2.5 g / 10 min, vinyl acetate monomer accounts for 45% by weight of the mixture of monomers.

Ammonium polyphosphate flame retardant II: Ammonium polyphosphate with melamine formalde coating, where n = 1200

Ammonium polyphosphate flame retardant I: Ammonium polyphosphate with melamine formalde coating, where n = 100

Property measurement and evaluation

Each specimen heat shrink tube was prepared as follows using the composition according to Examples (1 to 3) and Comparative Examples (1 to 5).

Each composition was kneaded at 120 ° C. for 10 minutes using a roll mill, and then pressed for 20 minutes at 170 ° C. to prepare a heat shrinkable tube specimen. For appearance evaluation and flame retardancy evaluation, the compound was processed at 120 ° C. using a kneader mixer, and then heat shrink tube samples were tested through a 45 mm pilot extruder.

The results of testing the mechanical properties, flame retardancy and appearance of the obtained Example and Comparative Example specimens are summarized in Table 2 below. Brief experimental conditions are as follows.

㉠ Mechanical properties at room temperature

High flame-retardant heat-shrinkable tubing must have a tensile strength of at least 1.06 kg / mm2 and an elongation of at least 200% at room temperature, subject to the conditions specified in the US UL 224 standard.

㉡ expandable

Tensile test at high temperature, 10 kg in / mm ² , the tensile modulus of heat shrink tubing products If it has the following values, it determines with pass. Specifically, the tensile strength when the elongation of the sample preheated at 170 ° C. for 5 minutes through a universal testing machine (UTM) is 15% is recorded. From this the tensile modulus is calculated.

㉢ flame retardant

In order to evaluate the flame retardancy of the high flame retardant heat shrink tube, the VW-1 vertical flame retardancy test according to the US UL 224 standard was performed. Specifically, after the flame was applied for 15 seconds, 15 seconds of fire extinguishing was repeated 5 times, and the total combustion time was evaluated based on not burning down within 60 seconds.

㉣ appearance

Evaluation of the appearance including color was evaluated by comparing the printing state of the extruded heat-shrink tube with the existing product.

Example number Comparative example number One 2 3 One 2 3 4 5 Room temperature
characteristic The tensile strength
(kg / mm2) 1.36 1.25 1.38 0.95 1.15 1.31 1.17 0.65 Elongation (%) 530 510 520 480 540 540 88 60 Inflatable
(kg / mm2) 1.2 1.5 1.4 2.0 1.3 1.2 28.8 1.3 Vertical flame retardancy
(VW-1) pass pass pass pass pass fail fail fail Appearance evaluation pass pass pass fail fail pass pass fail

As a result of measuring the physical properties as summarized in Table 2, the Example composition satisfies the reference value in VW-1 vertical flame retardancy, expandability, room temperature mechanical properties, and also excellent appearance and extrudability. However, Comparative Example 1, which contains 110 parts by weight of ammonium polyphosphate, did not meet the criteria in terms of room temperature tensile strength and appearance despite no difference in Example 1 and others. This is considered to be due to the dispersibility fall of a phosphorus flame retardant.

Comparative Example 2 is characterized by including a part of the EVA resin in the basic resin content of the vinyl acetate monomer exceeds the numerical range of the present invention. Room temperature mechanical properties, expandability and flame retardancy of Comparative Example 2 were excellent. However, although only a portion (20%) of the base resin, Comparative Example 2 included an EVA resin with an excess of vinyl acetate. Therefore, Comparative Example 2 failed in appearance evaluation. This is because the polarity of the resin increases with increasing vinyl acetate monomer content, thereby increasing the elasticity.

Comparative Examples 3 and 4 show how much the combination of the phosphorus-based flame retardant and the silicone-based auxiliary flame retardant of the present invention plays a role in the balance between mechanical properties and flame retardancy. Silicone-based auxiliary flame retardant was used only a small amount of 5 parts by weight in Example 1, but Comparative Example 3 lacking this silicone-based auxiliary flame retardant was not enough flame retardant. In Comparative Example 3, a drip phenomenon occurred in evaluating flame retardancy. Comparative Example 4 tried to increase the flame retardancy by using a large amount of metal hydroxide flame retardant, but due to the use of an excess metal hydroxide flame retardant mechanical properties are impossible to be processed into a heat shrink tube using a conventional process.

Comparative Example 5 is the use of ammonium polyphosphate of the crystal phase I, compared to the ammonium polyphosphate of the crystal phase II used in Example 1, the moisture absorption occurs much showed that the physical properties, flame retardancy, appearance all failed in evaluation.

From these results, it can be seen that the flame-retardant resin composition for heat-shrinkable tubes of the present invention not only has excellent balance between mechanical properties and flame retardancy, but also has excellent colorability.

As described above, optimal embodiments of the present invention have been disclosed. Although specific terms have been used in the specification including this embodiment, it is used only for the purpose of describing the invention in detail to those skilled in the art and used to limit the meaning or limit the scope of the invention described in the claims. It is not.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings attached to the present specification illustrate exemplary embodiments of the present invention, and together with the detailed description of the present invention, the present invention is intended to help understand the technical idea of the present invention. No.

1 is a cross-sectional view of a flame-retardant heat shrink tube for explaining an embodiment according to the present invention is a state in which the heat shrink tube is applied to the outer peripheral surface of the insert and contracted.

Claims (4)

Per 100 parts by weight of ethylene-vinyl acetate copolymer base resin; 30-100 parts by weight of a phosphorous flame retardant except red phosphorus; And 5 to 15 parts by weight of a silicone-based auxiliary flame retardant, The base resin is a resin composition for a heat-shrink tube comprising an ethylene-vinyl acetate copolymer having a melt index of 2 g / 10 min to 15 g / 10 min, polymerized using a vinyl acetate monomer in a proportion of 15 to 33% by weight. The method of claim 1, The phosphorus flame retardant is a resin composition for a heat shrink tube, characterized in that the ammonium polyphosphate represented by the formula (1). [Formula 1]

In Chemical Formula 1, n is an integer, and 1000 ≦ n ≦ 2000. The method of claim 2, The ammonium polyphosphate is a heat-shrink tube resin composition, characterized in that the polyammonium polyphosphate with melamine formalde coating. The heat shrink tube manufactured using the resin composition for heat shrink tubes of any one of Claims 1-3.

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