WO2002000807A1

WO2002000807A1 - Polyolefin-based hot melt adhesive for deflection yoke

Info

Publication number: WO2002000807A1
Application number: PCT/KR2001/000906
Authority: WO
Inventors: Soon-Cheol Choi; Ha-Seung Jung; Il-Won An
Original assignee: Seong Il Chemical Co., Ltd.
Priority date: 2000-06-24
Filing date: 2001-05-30
Publication date: 2002-01-03
Also published as: CN1441833A; AU6076901A; KR100314881B1; KR20000058683A

Abstract

A hot melt composition for a deflection yoke comprising as main components about 5 to 25% by weight of a polyethylene or polypropylene based wax component, about 25 to 40% by weight of a rosin based tackifying resin, about 10 to 50% by weight of an ethylene propylene copolymer based base polymer, about 1 to 10% by weight of a styrene based copolymer or block copolymer rubber, and at least one additional ingredient selected from the group consisting of fillers, plasticizers, antioxidants, flame retardants and colorants.

Description

POLYOLEFIN-BASED HOT MELT ADHESIVE FOR DEFLECTION YOKE

Technical Field The present invention relates to a polyolefin-type hot melt composition for a deflection yoke. Specifically, the main components of the polyolefin-type hot melt composition for a deflection yoke are: about 5 to 25% by weight of a polyethylene or polypropylene based wax component; about 25 to 40% by weight of a rosin based tackifying resin; about 10 to 50% by weight of an ethylene propylene copolymer based base polymer; about 3 to 10%ι by weight of a styrene based copolymer or block copolymer rubber; and at least one additional ingredient selected from the group consisting of fillers, plasticizers, anti-oxidants, flame retardants and colorants.

Background Art A deflection yoke is mounted on an outer surface of a rear glass envelope of a cathode ray tube (CRT) for adjusting an angle of deflection of electron beams emitted from an electron gun. The deflection yoke is one of the most important magnetic devices in the CRT and consists of a horizontal deflection coil, a vertical deflection coil and a ferrite core. A CRT is used as a Braun tube, which is a special vacuum tube for converting an electric signal into an optical image such as pictures, figures or characters by the action of electron beams. The CRT's basic application includes variety of image display devices, such as Braun tubes for a TV receiver or computer monitor, as well as industrial Braun tubes, such as an oscilloscope for calibrating electric phenomena or waveforms, a frequency analyzer, or a measurement Braun tube used for a screen monitor for medical treatments. A general Braun tube comprises of a fluorescent layer coated on the inner face of a panel of a glass envelope evacuated with a high degree of vacuum, a shadow mask and an electron gun. The electron gun generates heat from a heater by an externally applied voltage to radiate thermion from cathodes, thereby controlling, accelerating and focusing electrodes to impinge electron beams onto the fluorescent layer to emit light, forming an image. Here, the electron beams formed in the electron gun pass between two sets of deflection plates arranged at right angle or deflection coils and are deflected by a signal voltage externally applied to the deflection plates or deflection coils, so that bright spots on the fluorescent screen move up and down and left and right to draw an image. Deflection methods are roughly classified into electrostatic deflection in which electron beams are deflected by an electric field and electromagnetic deflection in which electron beams are deflected by a magnetic field by making current flow in deflection coils installed at the neck portion of a Braun tube. The electrostatic deflection is widely used in a measurement Braun tubes because of higher frequency in spite of a smaller angle of deflection, compared to the electromagnetic deflection.

Among the constituents of the deflection yoke, vertical deflection coils produce horizontal magnetic fields to deflect electron beams up and down, and horizontal deflection coils produce vertical magnetic fields to deflect electron beams left and right. In the case of the vertical deflection coils, the operation frequencies have been maintained at a relatively constant level of about 60 to 70 KHz. By contrast, in the case of the horizontal vertical deflection coils, the operation frequencies are about 15 KHz for conventional general-purpose TV receivers and about 48 KHz for recently developed HDTV's. In particular, computer monitors, generally used for a long time and requiring a very high resolution, operate at very high frequencies. Thus, deformation of the deflection yoke due to an increase in the temperature and a change in the screen characteristic has become a critical issue. Also, as Braun tubes have been in widespread use under a variety of climate conditions including hot, cold, dry, and humid climates, much attention is being paid to key properties of a deflection yoke such as cold resistance, heat resistance, adhesive strength, flame retardancy, thermal impact strength and so on.

In the deflection yoke, a hot melt is adhesively used for sealing and fixing a horizontal deflection coil, a vertical deflection coil and a ferrite core. A hot melt adhesive is a non-solvent type adhesive which has a solid content of 100% at room temperature. It is heated and molten when it is used, and adhered and applied to a matter to be adhered, followed by cooling to solidify, by which the adhesive strength is revealed. The hot melt adhesive has been widely used for packing, bookbinding or woodworking, as well as electric home appliances. Since the hot melt adhesive is heated at a high temperature and molten, followed by cooling immediately after being coated, a continuous process is allowed. Also, since no volatile content is generated, coating thickness can be easily controlled and uniform coating can be achieved. Also, the hot melt adhesive has less risk of a fire. Generally, the hot melt composition is composed of a base polymer, a tackifying resin and a wax. In some cases, an antioxidant, a plasticizer, a flame retardant or the like may be further added.

The hot melt adhesive comprises mainly of ethylene vinyl acetate (EVA) copolymer, and polyamide, polyester, atactic polypropylene have also been used as main components. Rosin based resins or petroleum resins used as the tackifier are mixed with the main component, and waxes, antioxidants, inorganic fillers or plasticizers may be further added in combination.

The hot melt adhesives are provided in various forms, for example, pellet, block and so on, and a desired form is selected according to usage or manner of use. If the temperature is lowered, the hot melt adhesive quickly adheres, usually within one second, thereby allowing a continuous adhesion process. Even a liquid adhesive can be suitably applied to complicated targets such as vertical planes or downwardly sloping planes. Because the hot melt adhesive exhibits the maximum adhesion strength immediately after being cooled, it can be used to materials that cannot be adhered by ordinary adhesives such as polyethylene or polypropylene.

However, the conventional hot melt adhesive generally used for packaging, bookbinding, woodworking, electric or electronic fields has several problems of heat resistance, cold resistance, adhesive strength, flame retardancy, heat impact and so on. Since the polyamides, which are main components of the conventional hot melt adhesive, are carbonized at a high temperature of 200°C or higher, the adhesive strength of the hot melt adhesive deteriorates. Also, the conventional hot melt adhesive has a drawback in that a property change is largely due to the absorption of polyamides. Low-density polyethylene used as a base material for an adhesive is very stiff because of its crystalline content, and undesirably exhibits a poor low temperature adhesion. Ethylene vinyl acetate is less compatible with other constituents, whereas its crystallinity is reduced. In addition, acryl has a poor adhesive strength, peeling resistance and creep resistance, and its applications are restricted to liquid or aqueous systems. Although use of the amorphous polyolefin improves thermal stability, the amorphous polyolefin exhibits inconsistent properties in view of class, composition and viscosity. Also, the amorphous polyolefin is very poor in adhesive strength and tensile strength due to a heterogeneous branch distribution and a wide molecular weight distribution, and tends to leave residues on the surface of a base after peeling. To overcome these drawbacks, the hot melt compositions with excellent bonding strength using relatively homogeneous linear ethylene/α-olefm copolymers have been proposed. However, since the proposed copolymers are composed of only polyolefin-based resins, they have poor low temperature adhesion and require high temperature formability, resulting in irregularities in foam materials and poor adhesive strength.

In particular, although the known hot melt compositions are mostly applied to various fields of paper or nonwoven industries and are widely used as adhesives of materials for automobile trim, they have not been satisfactory in terms of cold resistance, heat resistance and heat impact strength when they are applied to high- temperature heat generating deflection yokes, such as Braun tubes or monitors operating with high frequency. Accordingly, there has been an imperative need for a development of new hot melt compositions with a high-temperature heat resistance, a cold resistance and a heat impact strength, which are necessary properties for electric or electronic devices such as deflection yokes.

The present inventors researched intensively, and developed a hot melt composition for a deflection yoke which exhibits cold resistance at the lowest temperature of -40°C, heat resistance at the highest temperature of 120°C, and heat impact strength which is so strong not to result in cracking or flaking-off even with repetition of low-temperature and high- temperature heat impact cycles. The present inventors found that the developed hot melt composition had a good cold resistance, heat resistance and heat impact strength, and excellent properties in view of possibility of a continuous process and easy controllability of coating thickness. The composition comprises of about 5 to 25%> by weight of a polyethylene or polypropylene based wax component, about 25 to 40% by weight of a rosin based tackifying resin, about 10 to 50%> by weight of an ethylene propylene copolymer based base polymer, about 3 to 10% by weight of a styrene based copolymer or block copolymer rubber, and finally completed the present invention.

Disclosure of the Invention

It is an objective of the present invention to provide a polyolefin type hot melt composition with excellent cold resistance, heat resistance and heat impact strength.

It is another objective of the present invention to provide a hot melt composition for a deflection yoke with excellent cold resistance, heat resistance and heat impact strength so that it can be used for a Braun tube or monitor prone to deformation of the deflection yoke generating high-temperature heat due to high- frequency operation and a change in screen characteristic.

It is still another objective of the present invention to provide a hot melt composition for a deflection yoke which allows a continuous adhesion process by being heated at high temperatures to be molten and cooled and adhered immediately after being coated, and which is easy to evenly control the coating thickness because volatile content is not generated.

To accomplish the above objectives, the present invention provides a hot melt composition for a deflection yoke using polyolefin as a base material instead of polyamide.

In detail, the hot melt composition according to the present invention comprises of about 5 to 25% by weight of a polyolefin based wax component, about

25 to 40% by weight of a rosin based tackifying resin, about 10 to 50%) by weight of a polyolefin based ethylene propylene copolymer based base polymer, and about 1 to 10% by weight of a styrene based copolymer rubber.

Here, the polyolefin based wax component is preferably polyethylene or polypropylene based wax in an amount ranging from about 5 to 40% by weight to control the heat resistance and melting viscosity. Use of polyolefin wax component also improves workability. If the wax component used is less than 5% by weight, controlling the melting viscosity is difficult, the workability is inferior, and a hanging loop phenomenon occurs. If the wax component used is greater than 40% by weight, the adhesive strength is reduced and results in a poor low temperature adhesion characteristic.

The usable tackifying resins include natural or synthetic resins and their derivatives, such as rosin based resins, terpene based resins, petroleum resins and so on. In particular, use of rosin ester based hydrogenated resins or rosin phenol copolymer resins with the average molecular weight of 500 to 50,000 improve the adhesive strength. The amount of the tackifying resin used is preferably in the range from about 25% to about 40% by weight. The use of the rosin-based resins improves the adhesive strength, cold resistance and heat resistance. In order to increase cold resistance and heat resistance, polyolefin based copolymer-based base polymers are used. The base polymers used are preferably ethylene propylene copolymers having a weight average molecular weight of 500 to

50,000 in an amount of about 10 to 50%> by weight. In particular, the ethylene propylene copolymers preferably have a melting viscosity of 3,000 to 8,000 cps, a softening point of about 120 to 160°C, and a melting density of about 0.7 to 0.8 g/cm³.

Use of the polyolefin based copolymer based base polymers improves flexibility, cohesive strength and adhesive strength.

In order to improve cold resistance, rubber, such as styrene butadiene random copolymer (SBR), styrene butadiene block copolymer (SBS) or styrene ethylbutadiene copolymer (SEBS), is preferably used in an amount ranging from about 1 to 10%> by weight.

In addition, the hot melt composition according to the present invention may further include about 10 to 40%> by weight of a filler for absorbing shock, about 1 to

5% by weight of a plasticizer for improving flexibility and cold resistance, about 0.1 to 2% by weight of an anti-oxidant for maintaining stability against deformation due to UV rays or oxygen in the air, about 3 to 15% by weight of a flame retardant and about 0.2 to 3% by weight of a colorant.

Usable fillers include calcium carbonate or talcum. The plasticizer is an organic composition added to thermoplastic resins, rubber or other resins in order to improve extrusion adaptability, bendability, processability or flexibility, and examples thereof include paraffin or naphtene based hydrocarbon oil and polybutene. In particular, phthalic acid or polybutene-based plasticizers are preferably used in the present invention. Examples of the flame retardant used include halogens, phosphates and the like. In addition, antioxidants can be further added. The additional ingredients are generally inert and do not substantially affect the properties of the main components such as a base polymer, wax, tackifier and rubber. The additional ingredients are not limited to those described above and a variety of materials known in the art can be used for improving the performance of the hot melt composition according to the present invention.

The process of preparing a hot melt composition is largely divided into a step of heating component materials to be molten and blending the same and a step of molding and cutting into an appropriate size. The possible molding shapes include a pellet, chip, block, film and the like. In particular, in order to be applied to a deflection yoke according to the present invention, a chip-form hot melt composition is preferred but is not limited. To prepare the hot melt composition according to the present invention, various component materials are first heated and molten using a heat-melting agitation tank. A 100 to 5,000 liter tank is used for the heat-melting agitation tank. The melting temperature is in the range from about 100 to 250°C. A wax component and an anti-oxidant are injected into the tank at a rate of 20 to 150 rpm and molten while maintaining the temperature ranging from about 150 to 250°C. Thereafter, rubber is injected to be molten and then a tackifying resin is added to be molten, followed by blending.

When the main components are heated, molten and blended, a filler for absorbing shock and improving heat resistance is injected and diluted, and then a base polymer is dissolved. After the base polymer is completely molten, a plasticizer, a colorant and a flame retardant are sequentially injected and agitated for about 30 to 60 minutes to prepare the hot melt composition.

In a state in which the internal temperature of the agitation tank is maintained at about 150°C to about 250°C, a chip-form hot melt adhesive is prepared from the prepared hot melt composition using a steel conveyer belt.

In order to examine various characteristics of the hot melt adhesive for a deflection yoke using the hot melt composition according to the present invention, cold resistance, heat resistance, heat impact strength, adhesive property, flame retardancy and so on were evaluated.

First, in order to examine the cold resistance, the hot melt composition according to the present invention was molten to make test specimens and cooled to a room temperature. The test specimens were placed in constant temperature chambers maintained at temperatures of -20°C, -30°C, ~40°C, respectively, for about 168 hours, and then taken out to observe the occurrences of cracking or flaking-off by the naked eye. Cracking or flaking-off did not occur to the hot melt composition according to the present invention even at - 0°C. It was confirmed that the hot melt composition according to the present invention had a good cold resistance as to withstand at -40°C at a minimum.

In order to examine the heat resistance, the hot melt composition according to the present invention was put into a dry oven maintained at a high temperature and was allowed to stand for about 24 hours, followed by observing the degree of strain (carbonization) and the occurrences of precipitation. The observation result showed that little strain or precipitation occurred to the hot melt composition according to the present invention at 200°C, meaning that the hot melt composition according to the present invention had an excellent heat resistance compared to the conventional hot melt composition.

The heat impact strength was measured by allowing the hot melt composition according to the present invention to stand at a constant temperature and humidity chamber where low temperature and high temperature cycles were alternately repeated every hour for about 100 hours to observe cracking or flaking-off. The hot melt composition according to the present invention showed no occurrence of cracking and flaking-off even when the temperatures of the chamber were alternately changed over about 100 hours such that the chamber was held at about -40°C and at about 110°C, the each temperature maintenance time being about one hour in duration, that is, changes in temperature occurred 50 times. As a result, it was confirmed that the hot melt composition according to the present invention had excellent heat impact strength. The adhesive strength tests were carried out by measuring the maximum load such that test specimens were placed at a dry oven maintained at about 25°C for about one hour, taken out, and then pulled ^•within 10 seconds by a push pull gauge at a tensile rate of 10 mm/min until the test specimens were broken. As a result, the hot melt composition according to the present invention exhibited a tensile adhesive strength of about 70 to about 75 kgf/m², compared to known hot melt compositions exhibiting a tensile adhesive strength of about 55 kgf/m². The hot melt composition according to the present invention was better than the conventional hot melt composition, in view of the tensile adhesive strength. In order to examine the flame retardancy, the test specimens were placed in a flame retardancy tester and heated with flames for about 10 seconds to examine whether the flames were self-extinguished and after-flames occurred. The examination result showed that, whereas the conventional hot melt composition had two after-flames lasting 11 seconds or longer, the hot melt composition according to the present invention was completely self-extinguished without after-flames. That is an excellent performance so as to satisfy the UL-94 rating of V₀.

Brief description of the drawings

FIG. 1 depicts a deflection yoke specimen manufactured for testing cold resistance and heat impact strength of the hot melt composition for a deflection yoke according to the present invention, schematically showing the deflection yoke specimen manufactured by applying the hot melt composition to a joint portion of a pair of deflection yokes and a connecting portion of a plastic plate and deflecting coils: A: ferrite core

B: plastic plate C: part of applying hot melt D: deflection coil E: ferrite joint clip FIG. 2 is a schematic diagram of the test specimen manufactured for measuring the tensile adhesive strength of a hot melt composition for a deflection yoke according to the present invention, in which a portion marked by "O" on a "A" plane is secured on a fixed part and a portion marked by "O" on a "B" plane is secured on a push-pull gauge.

Best mode for carrying out the Invention

The invention will now be described in detail through the preferred embodiments. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein.

Example 1 : (1 ) Preparation of hot melt composition for deflection yoke

60 kg of polypropylene wax and 1.5 kg of an anti-oxidant were injected into a 500 L heat-melting agitation tank at a rate of 80 rpm at about 200°C. The wax and the anti-oxidant were molten in the agitation tank maintained at about 150°C to 250°C, followed by adding 6 kg of a styrene butadiene copolymer to be molten. After completely melting the components by stirring for about 2 hours, 55 kg of a rosin ester copolymer resin with a molecular weight between 1,000 and 15,000 was further added to be molten and admixed sufficiently.

87 kg of talcum as a filler was added and 64 kg of an ethylene propylene copolymer with a molecular weight between 1,000 and 10,000 was added as a base polymer to be melted.

After completely melting the base polymer, 5 kg of phthalic acid as a plasticizer, 18 kg of phosphate as a flame retardant were further added, followed by stirring for about 45 minutes. In the course of carrying out the process, the temperature of the agitation tank was maintained at about 150 to 250°C. After heating all the component materials to be molten, the resultant was cooled using a conveyer belt and manufactured as a chip-form hot melt composition.

Example ?^• (7.) Preparation of bot melt compngitirm for deflation ynk A hot melt chip was prepared in the same manner as in Example 1 using different kinds of wax, base polymer, rubber and tackifying resin. The components and contents of the respective compositions are listed in Table 1. Table 1. Hot melt composition and content

Experimental example 1 : Cold resistance test The hot melt compositions prepared in the examples were molten at about 180 to 220°C, applied to the deflection yokes to make the test specimens and cooled to a room temperature. The deflection yoke specimens were prepared by applying about 5 to 7 g of the hot melt composition to a joint portion of a pair of deflection yokes and a connecting portion of a plastic plate and deflecting coils (FIG. 1). The prepared specimens were placed in constant temperature chambers maintained at temperatures of-20°C, -30°C, - 0°C, respectively. After about 168 hours, occurrences of cracking or flaking-off were observed by the naked eye. The hot melt composition comprised of polyamide as a main base material was used as a reference group. The conventional hot melt composition had a cold resistance up to -20°C and exhibited cracking and flaking-off at -30°C or below. However, cracking or flaking-off did not occur to the hot melt composition according to the present invention even at -40°C. It was confirmed that the hot melt composition according to the present invention had such a good cold resistance as to withstand at -40°C at a minimum.

Experimental example 2: Heat resistance test 100 g of the hot melt composition according to the present invention was put into a crucible, formed of glass or iron, and was allowed to stand at a dry oven maintained at about 200°C for about 24 hours, followed by observing the degree of strain (carbonization) and the occurrences of precipitation. The degree of carbonization was determined by measuring the extent of carbonization of the specimen, i.e., the thickness of the carbonized region of the tested specimen.

The observation results showed that the hot melt composition according to the present invention had few precipitates and exhibited a very low degree of carbonization of about 1 mm or less.

Experimental example 3: Heat impact strength test

The hot melt composition according to the present invention was molten at about 180 to 220°C, coated on the deflection yokes to make the test specimens and cooled to a room temperature. The deflection yoke specimens were prepared by applying about 5 to 7 g of the hot melt composition to a joint portion of a pair of deflection yokes and a connecting portion of a plastic plate and deflecting coils (FIG. 1). The constant temperature chamber was set such that it was repeatedly held at about -40°C and at about 110°C, each temperature maintenance time being about one hour in duration. Then, the specimens were placed in the chamber and allowed to stand for 50 cycles (100 hours). After taking the specimens out from the chamber, the occurrences of cracking or flaking-off was examined.

The result showed that the hot melt composition according to the present invention showed no occurrence of cracking and flaking-off even when the temperatures of the chamber were at about -40°C (for about 1 hour) and at about 110°C (for about 1 hour), whereas the hot melt composition prepared in Comparative Example had heat impact resistance only at lower and upper limits of about -20°C (for about 1 hour) and at about 110°C (for about 1 hour). It was confirmed that the hot melt composition according to the present invention had excellent heat impact strength.

Experimental example 4: Tensile adhesive strength test

The hot melt composition according to the present invention was molten at about 180 to 220°C, applied to an adhesion surface of a prepared target to be coated within 5 seconds (FIG. 2) and allowed to stand at a room temperature for about one hour. The target was prepared by placing two specimens made of steel and each having a length of 100±0.5 mm and a width of 25±0.5 mm, such that one specimen lays over the other by 12.55±0.5 mm, and coating the hot melt adhesive therebetween. Thereafter, the test specimens were heated at a dry oven maintained at about 25 °C for about one hour. After one hour, the specimens were taken out and within 10 seconds a push pull gauge at a tensile rate of 10 mm/min measured the maximum load until the test specimens were broken. The measurement results are shown in Table 2.

Table 2. Tensile adhesive strength test

As shown in Table 2, the hot melt composition according to the present invention exhibited a tensile adhesive strength of about 70 to 75 kgf/m², compared to a known hot melt composition exhibiting a tensile adhesive strength of about 55 kgf/m². The hot melt composition according to the present invention was about 15 kgf/m² better than the conventional hot melt composition, in view of the tensile adhesive strength. Experimental example 5: Flame retardancy test

The hot melt composition according to the present invention was molten at about 180 to 220°C, and made the test specimens having a width of 125.0 mm, a length of 12.7 mm and a depth of 2.5 mm. Five specimens were placed in a constant temperature and humidity held at 23±2°C and 50±5%>. Thereafter, the specimens were allowed to stand in a dry oven held at about 70±1°C, for about 168 hours and in a decicator for about 4 hours, for pretreatment (see UL flammability standard 94 8.3.2). The specimens were fixed at positions of 6 mm from upper ends by means of clamps in a flame retardancy tester, The height from the upper ends to the bottom surface was adjusted to 300 mm, The intervals between each of the respective specimen were 10 mm, The burner was inclined at an angle of 45 degrees and the lengths of flames were set to 20±1 mm. The bottom of the tester was covered with cotton of 50 mm in width, 50 mm in length and 6 mm in depth. Flames were applied to each of the specimens for about 10 seconds and then the burner was allowed to self- extinguish. A time required until the flames were self-extinguished since afterflames occurred to the specimen, i.e., t_l5 was measured. Then, after the heights of the specimen and the burner were adjusted, flames were applied to the same specimen and then the burner was extinguished. A time required until the flames were self- extinguished since afterflames occurred to the specimen, i.e., t₂, was measured. Then, when the afterflames in the specimen were self-extinguished and afterglows were generated, a time required until the afterglows vanished, i.e., t₃, was measured. This procedure was carried out in the same manner with respect to the other four specimens (see UL flammability standard 94 8.5). In accordance with the standards of UL 94 8.1 ratings, the flame retardant properties of the specimens coated with the hot melt composition prepared in the comparative example and the hot melt composition according to the present invention, were investigated. The standards of UL 94 8.1 ratings are listed in Table 3, and the flame retardancy test results are shown in Table 4. Table 3: Standards of UL 94 8.1 ratings

Table 4: Flame retardancy test results

The test results showed that, the two specimens prepared in the comparative example had after-flames for over 11 seconds, that is, the UL 94-V₀ standard was not satisfied; however, the hot melt composition according to the present invention was self-extinguished immediately after heating and extinguishing the burner and, the UL 94- V₀ standards were satisfied (see the standards of UL 94 8.1 ratings).

Industrial Applicability

The hot melt composition according to the present invention has excellent adhesive strength, shock absorbance and flame retardancy, and its cold resistance, heat resistance and heat impact strength, which are essentially required to be used for deflection yokes in the electric/electronic field, are superior to the conventional general-purpose hot melt composition. Accordingly, the hot melt composition according to the present invention is effective in prolonging the life span of a Braun tube or monitor, enhancing operational reliability, preventing short-circuiting due to overheating and extending the usability under various severe weather conditions. Therefore, the hot melt composition according to the present invention can be effectively used for deflection yokes necessitating high levels of cold resistance, heat resistance and heat impact strength, thereby improving the quality of a Braun tube.

Claims

What is claimed is:

1. A hot melt composition comprising of: about 5 to 25% by weight of a polyolefin based wax component; about 25 to 40% by weight of a rosin based tackifying resin; about 10 to 50% by weight of an ethylene propylene copolymer based base polymer; and about 1 to 10%) by weight of a styrene based copolymer rubber.

2. The hot melt composition according to claim 1, wherein the polyolefin based wax component is polyethylene or polypropylene based wax.

3. The hot melt composition according to claim 1 , wherein the rosin based tackifying resin is a rosin ester based hydrogenated resin or rosin phenol copolymer resin.

4. The hot melt composition according to claim 3, wherein the rosin phenol copolymer resin has a weight average molecular weight of 500 to 50,000.

5. The hot melt composition according to claim 1, wherein the ethylene propylene copolymer has a weight average molecular weight of 500 to 50,000.

6. The hot melt composition according to claim 5, wherein the ethylene propylene copolymer has a melting viscosity of 3,000 to 8,000 cps, a softening point of about 120 to 160°C, and a melting density of about 0.7 to 0.8 g/cm³.

7. The hot melt composition according to claim 1, wherein the styrene based copolymer rubber is one selected from the group consisting of styrene butadiene random copolymer (SBR), styrene butadiene block copolymer (SBS) and styrene ethylbutadiene copolymer (SEBS)

8. The hot melt composition according to claim 1, further comprising at least one of about 10 to 40%» by weight of a filler, about 1 to 5% by weight of a plasticizer, about 0.1 to 2%o by weight of an anti-oxidant, about 3 to 15%ι by weight of a flame retardant and about 0.2 to 3% by weight of a colorant.

9. The hot melt composition according to claim 8, wherein the filler is a calcium carbonate or talcum.

10. The hot melt composition according to claim 8, wherein the plasticizer is a phthalic acid or polybutene based plasticizer.

11. The hot melt composition according to claim 8, wherein the flame retardant is halogen or phosphates.

12. The hot melt composition according to claim 1, wherein the hot melt composition comprises of: about 10 to 20%) by weight of a polyethylene wax; about 30 to 35% by weight of a rosin ester copolymer based tackifying resin; about 10 to 30% by weight of an ethylene propylene copolymer based base polymer; and about 2 to 8%> by weight of a styrene butadiene block copolymer rubber,.