Hot melt composition and use thereof

A hot melt composition including 100 parts by weight of a styrene thermoplastic elastomer having an intrinsic viscosity [.eta.] of not less than 1 dl/g and 200 to 3000 parts by weight of a liquid softener selected from process oil, liquid rubber and a modified substance thereof, wherein: PA1 (a) the composition has a softening point measured by ring and ball softening pint method of from 120 to 230.degree. C.; PA1 (b) the composition generates no crack when not less than 75% of a compressive strain is applied under an atmosphere of a temperature of -30 to 40.degree. C.; and PA1 (c) the composition does not flow when it is allowed to stand in a load-free state under an atmosphere of a temperature of 100.degree. C. for 24 hours. When the amount of the liquid softener mixed is from 500 to 1200 parts by weight, the composition is particularly useful for industrial sealing material, and when the amount is from 1200 to 3000 parts by weight, the composition is particularly useful for buffer material or vibration isolating material.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a hot melt composition and more
 particularly to a hot melt composition, which inhibits brittleness at low
 temperature and fluidity at high temperature and is superior in
 flexibility, and which has adhesion and easy release to the adherend and
 also has excellent suitability for buffer material, vibration-isolating
 material or industrial sealing material.
 2. Description of the Prior Art
 With recent rapid progress of a polymer synthesis technology, functional
 plastics and elastomers, which are superior in balance between cost and
 performance, have been intensively marketed in place of a conventional
 material in any industrial field.
 For example, in the metal substitution filed to which heavy-duty
 characteristics at high temperature are required, a share of
 thermoplastics having excellent moldability has rapidly been enlarged,
 excluding a part of thermosetting resins. On the other hand, in the field
 of a rubber product, a conventional vulcanized rubber produced by kneading
 a raw rubber, a reinforcer and a vulcanizing agent and then passing
 through a step of molding and vulcanization, using much labor and energy
 is obliged to be withdrawn or isolated from a part of application fields
 at present because of the advent of a thermoplastic elastomer which can be
 molded or shaped by using a molding machine for thermoplastics.
 Heretofore, various sealing materials have been used to maintain sealing
 properties of the bonded portion of containers, building structures,
 various molding machines or the like.
 As the sealing material, materials having characteristics such as rubber
 elasticity are often used, and formerly, molded articles of vulcanized
 rubber, soft vinyl chloride resin, polyurethane or the like was used.
 Recently, hot melt type elastomer polymers have been used.
 Furthermore, in the application field for sealing material to which
 rubber-like properties are required at high temperature, cost reduction is
 not effected, since it is troublesome to fit vulcanized molded articles
 and synthetic resin foamed articles and it is also difficult to perform
 automation. Therefore, attempts for practical application of a hot melt
 type sealing material of a thermoplastic elastomer has gradually been made
 which can be molten and fit at a job site.
 In a conventional hot melt mixing system, since a low-molecular weight or
 moderate-molecular weigh elastomer is basically used as a base polymer,
 the shape becomes unstable at high temperature range and fluidization can
 not be avoided. It is a technical common knowledge to add a compound of
 wax having a structural viscosity in order to prevent fluidization.
 However, when wax is added, the flexibility is considerably lowered,
 resulting in poor balance between the heat resistance and flexibility.
 Therefore, such an elastomer is not suitable for applications such as
 sealing material. Since the moderate/low-molecular weight elastomer is
 used as a base, initial tack is excellent. However, the release properties
 become poor to cause a problem that it becomes difficult to release from
 the adherend after use.
 In addition, since the molecular weight of the base polymer is low, the
 softening temperature is low and the heat resistance is poor. When the
 liquid softener is added to impart the flexibility, mechanical
 characteristics at high temperature are lowered to cause a phenomenon that
 fluidization is caused by its own weight in the range at 50.degree. C. or
 higher or large compressive permanent strain is remained when compressed.
 These characteristics are not suitable for applications such as sealing
 material to which sealing properties at higher temperature are required.
 In an elastomer hot melt mixing system, process oil is generally added to
 impart the flexibility. As the amount of the process oil increases, the
 compressive permanent strain becomes larger. Accordingly, also in this
 case, a balance between the flexibility and compressive permanent strain
 is poor and the suitability as the sealing material is lowered.
 Even in case of a styrene block copolymer which is considered to have
 excellent restoring properties among hot melt type systems, sufficient
 sealing properties can not be maintained, since the polymer having the
 composition used at present exhibits considerably large compressive
 permanent strain at high temperature. Therefore, it can not be applied to
 practical use.
 In a hot melt composition using a conventional styrene thermoplastic
 elastomer, there can be used, as a basic mix, those prepared by using an
 elastomer having an intrinsic viscosity [.eta.] measured in decalin at
 135.degree. C. of less than 1 dl/g as a base and adding a liquid softener
 such as oil, liquid rubber or the like in the amount of about 20 to 200
 parts by weight based on the 100 parts by weight of the elastomer.
 As other sealing materials using the elastomer, for example, Japanese
 Patent Kokai Publication No. 4-110381 discloses a hot melt gasket
 composition comprising 50 to 100 parts by weight of a reactive elastomer
 of a carboxyl-modified styrene-ethylene-butylene-styrene block copolymer
 or a styrene-butadiene-styrene block copolymer, and 50 to 250 parts by
 weight of a softener comprising a process oil.
 This invention discloses as follows. That is, when the amount of the
 softener is less than 50 parts by weight, the viscosity of the mixture
 becomes extremely high, resulting in poor machinability and workability.
 On the other hand, when the amount exceeds 250 parts by weight, the
 workability and heat resistance become poor.
 In the Examples, the followings are specifically described. That is, a
 styrene block copolymer used as a reactive elastomer is a
 carboxyl-modified styrene thermoplastic elastomer having an [.eta.] value
 of 0.67. A composition obtained by mixing a two-fold amount of paraffin
 oil with this styrene block copolymer and further mixing a synthetic wax,
 a low-density polyethylene, an ethylene-vinyl acetate copolymer, a
 nonionic surfactant or silicone oil for releasing as an optional component
 is superior in close-contact and adhesion to an iron plate.
 As described above, an object of the above prior art is to provide a gasket
 composition for enhancing close adhesion to an iron plate, and the used
 reactive ethylene monomer is characterized by being a comparatively
 low-molecular weight styrene block copolymer.
 As described above, since the conventional sealing material and caulking
 material including those of the above prior art use a moderate- or
 low-molecular weight elastomer as the base, basically, not only the
 softening point is low and fluidization arises at high temperature, but
 also the compressive permanent strain, particularly compressive permanent
 strain at high temperature, is large. Therefore, they are not preferred as
 the sealing material in view of the suitability.
 To prevent fluidization, wax for imparting a structural viscosity has been
 added. In that case, the flexibility is lowered, resulting in a mix having
 properties which are brittle and liable to be broken.
 Large compressive permanent strain means poor restoring force against
 loading. Since such a material is plastically deformed in the loaded
 state, when vibration is applied with a lapse of time, there arises a
 problem that a gap is gradually formed between the material and a member
 to be sealed and a good sealed state can not be maintained for a long
 period.
 With recent requirement of recycling of materials and gentleness to global
 environment, objects for disposal as an industrial waste must be discarded
 after separating them by the kind of materials as possible. However, it is
 difficult to separate a gasket adhered firmly onto the adherend such as
 iron member, like the above prior art. Therefore, the iron member and
 gasket, which are respectively made of different materials, are discarded
 as they are without being separated, resulting in one of causes of
 environmental disruption.
 SUMMARY OF THE INVENTION
 Hence, it is an object of the present invention to provide a hot melt
 composition, which exhibits small compressive permanent strain at high
 temperature and is superior in close adhesion to the adherend, but is
 easily released from the adherend and suitable for industrial sealing
 material.
 It is another object of the present invention to provide a hot melt
 composition, which inhibits brittleness at low temperature and fluidity at
 high temperature and has flexibility.
 It is yet another object of the present invention to provide a hot melt
 composition, which can be applied as an industrial sealing material,
 buffer material or vibration isolating material, which shows various
 sealing characteristics according to the amount of the liquid softener and
 addition of other optional agents to be mixed.
 The present invention has been investigated to accomplish the above
 objects, and it comprises, as a base mix, a hot melt composition
 characterized by the fact that it is obtained by mixing a specific
 high-molecular weight styrene thermoplastic elastomer with a large amount
 of a liquid softener.
 The present invention provides a hot melt composition comprising 100 parts
 by weight of a styrene thermoplastic elastomer having an intrinsic
 viscosity [.eta.] of not less than 1 dl/g and 200 to 3000 parts by weight
 of a liquid softener selected from process oil, liquid rubber and
 amodified substance thereof, characterized in that:
 (a) said composition has a softening point measured by the ring and ball
 softening point method from 120 to 230.degree. C.;
 (b) said composition generates no crack when not less than 75% of a
 compressive strain is applied under an atmosphere of the temperature of
 -30 to 40.degree. C.; and
 (c) said composition does not flow when it is allowed to stand in a
 load-free state under an atmosphere of the temperature of 100.degree. C.
 for 24 hours.
 In addition, the present invention provides the hot melt composition as
 described above, wherein the styrene thermoplastic elastomer is at least
 one selected from the group consisting of styrene-isoprene-styrene block
 copolymers, styrene-butadiene-styrene block copolymers and hydrogenation
 products thereof as well as carboxyl-modified styrene elastomers.
 Moreover, the present invention provides the hot melt composition as
 described above, wherein the amount of the liquid softener mixed is from
 300 to 3000 parts by weight based on 100 parts by weight of the styrene
 thermoplastic elastomer.
 Yet, the present invention provides the hot melt composition as described
 above, wherein the amount of the liquid softener mixed is from 500 to 1200
 parts by weight based on 100 parts by weight of the styrene thermoplastic
 elastomer.
 Still, the present invention provides the hot melt composition as described
 above, wherein the amount of the liquid softener mixed is from 1200 to
 3000 parts by weight based on 100 parts by weight of the styrene
 thermoplastic elastomer.
 Yet, the present invention provides the hot melt composition as described
 above, wherein the melting point is from 130 to 220.degree. C.
 Still, the present invention provides the hot melt composition as described
 above, wherein a rosin and/or petroleum resin tackifier is further added.
 Yet, the present invention provides an industrial sealing material using
 the hot melt composition as described above.
 Still, the present invention provides a buffer or vibration-isolating
 material using the hot melt composition as described above.
 DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The greatest feature of the present invention lies in use of a styrene
 elastomer having high molecular weight as a base polymer constituting the
 hot melt composition, and in mixing of a comparatively large amount of a
 liquid softener. A technical meaning lies in the respect that a hot melt
 composition having remarkably strong cohesive force, which has never been
 obtained by a conventional hot melt composition, could be obtained by the
 above feature.
 The composition of the present invention is remarkably superior in release
 properties to the adherend when applied to the field of the sealing
 material because a high-molecular weight elastomer is used as a base. The
 composition also has a function of easy demolition, capable of easily
 releasing the sealing material from the adherend, and excellent
 rubber-like properties at high temperature. These facts are considered to
 be the grounds for enhanced sealing performances to the adherend.
 In the present invention, it is important that the styrene elastomer used
 as the base polymer has an intrinsic viscosity [.eta.] of not less than 1.
 When [.eta.] is not less than 1, not only a single elastomer but also a
 blend of a plurality of elastomers may be used. The term "intrinsic
 viscosity [.eta.]" used in the present invention refers to a value
 measured in decalin at 135.degree. C.
 Selection of this base polymer has a critical meaning decided by extensive
 studies conducted by the present inventors, and its effect is apparently
 distinguished from the effect of the styrene elastomer having an intrinsic
 viscosity [.eta.] of less than 1 used as a sealing material.
 The styrene thermoplastic elastomer is not particularly limited insofar as
 it has an intrinsic viscosity [.eta.] of not less than 1. Examples thereof
 include styrene/butadiene block copolymer (S-B), (S-B-S), styrene/isoprene
 block copolymer (S-I), (S-I-S), styrene/butadiene-isoprene block copolymer
 (S-B.I), (S-B.I-S), hydrogenated products of these block copolymers, for
 example, a hydrogenated product of styrene-butadiene-styrene block
 copolymer (SEBS), a hydrogenated product of styrene-isoprene-styrene block
 copolymer (SEPS), and hydrogenated product. The styrene block may include
 copolymer of aromatic vinyl compound, such as one from styrene and
 .alpha.-methylstyrene, in addition to polystyrene.
 Among these styrene thermoplastic elastomers, styrene-isoprene-styrene
 block copolymers, styrene-butadiene-styrene block copolymers and
 hydrogenated products thereof as well as hydrogenated products are
 preferably used.
 The proportion of the styrene system in these styrene elastomers is from 5
 to 70% by weight. When the proportion is from 20 to 40% by weight, a
 balance between the flexibility at high temperature and rubber elasticity
 is excellent.
 In the present invention, it is important to mix this specific base polymer
 with a large amount, i.e., 200 to 3000 parts by weight, of the liquid
 softener. Since the base polymer is a highmolecule, the resulting polymer
 is superior in characteristics such as sealing characteristics, easy
 release, buffer property, vibration isolating property and the like.
 It is preferred that the hot melt composition of the present invention
 concurrently has the following physical properties:
 (a) a softening point measured by the ring and ball softening point method
 is from 120 to 230.degree. C.;
 (b) no crack arises when not less than 75% of a compressive strain is
 applied under an atmosphere of the temperature of -30 to 40.degree. C.;
 and
 (c) the composition does not flow when it is allowed to stand in a
 load-free state under an atmosphere of the temperature of 100.degree. C.
 for 24 hours.
 The characteristics as the sealing material vary depending on the amount of
 the liquid softener, thereby making it possible to provide a sealing
 material capable of coping with various variations including the kind and
 shape of the adherend, site of use, and temperature condition.
 The sealing material in the present invention means those, which can be
 suited for all sealing materials such as gasket, packing, sealing,
 caulking, putty and the like.
 The softening point of the hot melt composition of the present invention is
 from 120 to 230.degree. C., preferably from 130 to 220.degree. C., and
 particularly from 150 to 200.degree. C. The high temperature suitability
 of the composition of the present invention depends largely on the
 molecular weight of the styrene elastomer as the base elastomer. However,
 these characteristics depend exclusively on how a styrene domain
 constituting a skeleton of a matrix can tolerate the load applied from the
 outside. When the molecular weight of the polystyrene constituting the
 styrene domain is low, attack on the domain by a large amount of the
 liquid softener proceeds and the heat resistance is lowered. Accordingly,
 it is impossible to secure the heat resistance only by the molecular
 weight of the elastomer, and the thermal properties are decided by the
 liquid softener and elastomer.
 In general, when the amount of the liquid softener added is increased, the
 flexibility is enhanced, however, the softening point is lowered and the
 heat resistance is deteriorated. On the other hand, when the amount of the
 liquid softener added is decreased, the softening point is raised and the
 high temperature characteristics are improved, however, the resulting
 composition is liable to become brittle at normal temperature and low
 temperature.
 The ring and ball method is a method of measuring the softening point
 according to JAI-17-1991.
 Regarding the sealing material of the present invention, it is necessary
 that no crack arises when not less than 75% of a compressive strain is
 applied under an atmosphere of the temperature of -30 to 40.degree. C.
 This compressive permanent strain means that no crack arises at the time
 when a load is released under this condition immediately after
 compression. If no crack arises even under such condition, a sealing
 material having high sealing properties can be obtained.
 It is important that the sealing material of the present invention does not
 flow when it is allowed to stand in a load-free state under an atmosphere
 of the temperature of 100.degree. C. for 24 hours. This provision is
 important for providing accurate setting as the sealing material even if
 the adherend is placed under high temperature. A sealing material which
 flows under an atmosphere at 100.degree. C. is not suitable to perform a
 sealing material fitting operation under a high temperature atmosphere.
 In the present invention, the liquid softener to be mixed with styrene
 elastomer include, for example, at least one selected from the group
 consisting of process oil, liquid rubber and modified substances thereof.
 In order to preferably accomplish the object of the present invention,
 there can be used process oils such as paraffin oil, naphthene oil,
 aromatic oil and the like; or liquid rubbers such as liquid polyisoprene,
 liquid polybutadiene, liquid polybutene, liquid 1,2-polybutadiene, liquid
 styrene-butadiene rubber, maleic polybutadiene, terminal hydroxyl
 group-containing polybutadiene, maleic polybutene and the like, alone or
 in combination thereof.
 It is possible to use components, which can be normally used as the liquid
 tackifier, such as rosin ester, modified rosin ester, terpene oligomer,
 modified terpene oligomer, C.sub.5 liquid petroleum resin, C.sub.5
 -C.sub.9 liquid petroleum resin and the like, as the liquid softener of
 the present invention. When using this liquid tackifier, the adhesion to
 the adherend is further improved and it becomes difficult to release from
 the adherend after use. Accordingly, this tackifier may not be used for
 application to which easy release is required.
 The amount of the liquid softener to be mixed varies depending on the kind
 and state of the adherend. In order to accomplish the object of the
 present invention, i.e. excellent adhesion and excellent release from the
 adherend, the liquid softener is mixed in the amount within the range from
 200 to 3000 parts by weight based on 100 parts by weight of the styrene
 elastomer. The sealing characteristics of the hot melt composition
 obtained vary depending upon the mixing amount of the liquid softener.
 That is, as the amount of the liquid softener increases, the flexibility
 of the composition is generally enhanced and the adhesion to the adherend
 is improved. It should be understood, however, that the reason why the
 composition of the present invention exhibits excellent sealing
 characteristics at high temperature is as follows. That is, since not only
 the sealing material becomes soft but also the high temperature impact
 resilience has been large for a long period of time, the pressure of the
 contact surface between the adherend and sealing material is always
 maintained at high level.
 In fact, as will be apparent from the Examples described hereinafter, it
 can be understood that there is the range having excellent balance between
 the amount of the liquid softener and impact resilience.
 In the present invention, the composition becomes useful as the sealing
 material, buffer material and vibration isolating material, by mixing the
 liquid softener in the amount of 200 to 3000 parts by weight based on 100
 parts by weight of the styrene thermoplastic elastomer. Particularly, when
 the liquid softener is mixed in the amount of 500 to 1200 parts by weight
 based on 100 parts by weight of the styrene thermoplastic elastomer, the
 balance between the compressive permanent strain at high temperature and
 rubber-like impact resilience is excellent as the characteristics of the
 sealing material. When the liquid softener is mixed in the amount of 1300
 to 3000 parts by weight based on 100 parts by weight of the styrene
 thermoplastic elastomer, the resulting sealing material becomes soft and
 the compressive stress is considerably lowered, however, the shape
 retention is excellent and fluidization does not occur. Consequently,
 functions such as buffer property and vibration isolating property are
 exhibited.
 When the amount of the liquid softener is from 1300 to 3000 parts by
 weight, there is a mixing range having remarkable flexibility enough to
 exhibit very low compressive stress value of not more than 0.1 kg/cm.sup.2
 under 50% compression at normal temperature, and shape retention enough to
 cause little compressive permanent strain at normal temperature. These
 characteristics are suitable for hot melt type buffer material and
 vibration isolating material.
 Since the base polymer of the present invention has a molecular weight
 higher than that of a base polymer of a conventional hot melt composition,
 it is basically superior in heat resistance as amatter of course.
 Surprisingly, it has also been found that, even if the flexibility is
 imparted by adding much amount of the liquid softener, not only mechanical
 characteristics at high temperature, particularly compressive permanent
 strain is not increased, but also a remarkably low value is exhibited in a
 certain range of adding amount.
 The reason is assumed that a matrix having interlocked high-molecular
 weight elastomer molecules embraces a large amount of the low-molecular
 weight liquid softener, thereby to develop characteristics which can not
 be understood by extension of the conventional concept.
 Anyway, it is apparent that the above specified hot melt composition of the
 present invention is a material having remarkably excellent
 high-temperature sealing function by maintaining the rubber-like impact
 resilience even at high temperature, and has excellent suitability as the
 industrial material.
 Examples of the buffer material include semi-liquid one such as gel and
 solid one such as reactive foam or reactive type one. The mix of the
 present invention has the following merits. That is, it is not necessary
 to place in a container because it is a solid hot melt. Since an aging
 time is a cooling time, the working time can be reduced in comparison with
 the reactive type one. Furthermore, since it is a hot melt, the hot melt
 is molten and formed into an arbitrary shape at a job site.
 As described above, the hot melt composition of the present invention is
 superior in capability of retaining the liquid softener because the base
 polymer has high molecular weight. Therefore, it becomes possible to
 retain the solid state even if a large amount of the liquid softener is
 added. Also, the hot melt composition of the present invention can exhibit
 the flexibility, which is not recognized in a conventional hot melt
 composition.
 In case of the base polymer composition wherein [.eta.] is less than 1.0,
 it is difficult to retain the solid state when the amount of the softener
 added is within the above range. Even if the solid state can be obtained,
 compressive permanent strain at high temperature is large and the shape
 retention is poor. Therefore, it can not be used as the buffer material or
 vibration isolating material like the present invention.
 In order to further improve the adhesion, tackifiers can be added to the
 hot melt composition of the present invention. As the tackifier, there can
 be used tackifiers known per se such as alicyclic hydrogenated tackifier,
 rosin, modified rosin, esterified products thereof, aliphatic petroleum
 resin, alicylic petroleum resin, aromatic petroleum resin, a copolymerized
 petroleum resin of an aliphatic component and an aromatic component,
 low-molecular weight styrene resin, isoprene resin, alkylphenol resin,
 terpene resin, coumaronindene resin and the like without any limitation.
 Among them, rosin and/or petroleum resin tackifiers are preferably used.
 It is possible to mix modifiers such as polyolefin wax and the like,
 inorganic and/or organic fillers, or additives such as pigments,
 stabilizers and the like as far as the object of the present invention is
 not adversely affected.
 Examples of the wax include paraffin wax, microcrystalline wax,
 polyethylene wax, polypropylene wax, Fisher-Tropsh wax, polyethylene oxide
 wax, meleic polyethylene wax and modified products thereof.
 Examples of the thermoplastic elastomer and thermoplastic resin include
 styrene-butadiene rubber, ethylene-propylene rubber, butyl rubber, acrylic
 rubber, ethylene-vinyl acetate copolymer, polyethylene, polypropylene,
 polystyrene, polybutene, polybutadiene and the like.
 Examples of the inorganic filler include calcium carbonate, zinc oxide,
 glass beads, titanium oxide, alumina, carbon black, clay, ferrite, talc,
 mica powder, aerogyl, silca, inorganic fiber such as glass fiber,
 inorganic foam and the like.
 Examples of the organic filler include powder of thermosetting resin such
 as epoxy resin, carbon fiber, synthetic fiber, synthetic pulp and the
 like.
 Examples of the stabilizer include phenolic antioxidant, phosphorus
 antioxidant, benzotriazole ultraviolet absorber, benzophenone ultraviolet
 absorber, hindered amine radical scavenger and the like.

EXAMPLES
 The following Examples further illustrate the present invention but are not
 to be construed to limit the scope thereof.
 Production of test pieces in the Examples and Comparative Examples as well
 as evaluation of physical properties of hot melt compositions were
 performed according to the following methods.
 &lt;Method of measuring softening point&gt;
 This was measured according to JAI-17-1991.
 &lt;Method of producing compression test piece&gt;
 A cylinder having a height of 20 mm and a diameter of 27 mm was molded from
 the resulting hot melt composition and was used as a compression test
 piece.
 &lt;Method of evaluating crack under compression&gt;
 Using an accurate universal testing machine equipped with a constant
 temperature bath (Autograph AG-2000C, manufactured by Shimadz Seisakusho
 Co.), a compression test piece was compressed in the height direction by
 75% at a compression rate of 50 mm/min in a measuring atmosphere at -30
 and 40.degree. C., and then released immediately. It was visually observed
 whether crack occurs or not. The evaluation was performed by the following
 criteria. .smallcircle.: No crack was observed; X: Crack was observed.
 &lt;50% compressive stress&gt;
 The test piece was compressed in the same manner as that of the method of
 evaluating crack under compression, and the compressive stress at this
 time was measured. Stress/Sectional area=Compressive stress (kg/cm.sup.2).
 &lt;50% compressive strain&gt;
 The same test piece as described above was compressed by 50% (compressed
 from 20 mm to 10 mm) and allowed to stand at 80.degree. C. for 24 hours.
 After standing, the test piece was released and the height after 22 hours
 was measured. Permanent strain was measured by the following calculating
 equation.
 ##EQU1##
 &lt;Method of evaluating fluidity under unloaded state&gt;
 The same test piece as that of the compression test specimen was allowed to
 stand under an unloaded state in a constant temperature bath at an
 atmospheric temperature of 100.degree. C. for 24 hours so that the height
 direction of the test piece is perpendicular to the horizontal surface.
 After standing, the test piece was removed and then the fluidity was
 evaluated by the following criteria. .smallcircle.: No fluidity, that is,
 the case where a projected area of the bottom surface of the test piece is
 less than 10% of that before standing; X: With fluidity, that is, the case
 where a projected area of the bottom surface of the test piece is not less
 than 10% of that before standing.
 &lt;Water tightness&gt;
 A hot melt composition was applied on the glass surface in the form of a
 circle (bead having a width of about 1 cm and a height of about 0.3 cm)
 and was dipped in water at 80.degree. C. and allowed to stand for 10 days
 in the state of being compressed by 50% between the glass plate and
 another glass plate. Then, it was confirmed whether water penetrates or
 not. The evaluation was performed by the following criteria.
 .smallcircle.: Penetration of water was not observed; X: Penetration of
 water was observed.
 &lt;Example 1&gt;
 To 200 parts by weight of SEPS (referred to as Elastomer a) having [.eta.]
 of 1.46 as a styrene elastomer, 600 parts by weight of "Diana Process Oil
 PW-90" (manufactured by Idemitsu Kosan Co. Ltd.) and the mixture was
 charged in a 1 liter twin-arm type kneader manufactured by Moriyama Co.
 (model SVI-1GH-E). After kneading at 52 rpm at 200.degree. C. for 1 hour,
 about 800 g of a hot melt composition was obtained.
 The physical properties of the resulting hot melt composition are shown in
 Table 1.
 &lt;Example 2&gt;
 According to the same manner as that described in Example 1 except for
 changing the amount of the styrene elastomer in Example 1 to 100 parts by
 weight and changing the amount of the liquid softener ("Diana Process Oil
 PW-90") to 500 parts by weight, about 600 g of a hot melt composition was
 obtained. The physical properties of the resulting hot melt-composition
 are shown in Table 1.
 &lt;Example 3&gt;
 According to the same manner as that described in Example 2 except for
 using 100 g of SEPS (referred to as Elastomer b) having [.eta.] of 1.26 as
 the styrene elastomer, about 600 g of a hot melt composition was obtained.
 The physical properties of the resulting hot melt composition are shown in
 Table 1.
 &lt;Comparative Example 1&gt;
 According to the same manner as that described in Example 1 except for
 using 200 g of SEBS (referred to as Elastomer c) having [.eta.] of 0.59 as
 the styrene elastomer, a hot melt composition was obtained.
 The physical properties of the resulting hot melt composition are shown in
 Table 1.
 &lt;Comparative Example 2&gt;
 According to the same manner as that described in Example 2 except for
 using 100 g of Elastomer c having [.eta.] of 0.59 as the styrene
 elastomer, a hot melt composition was obtained. The physical properties of
 the resulting hot melt composition are shown in Table 1.
 &lt;Examples 4 to 5 and Comparative Examples 3 to 5&gt;
 As Examples, hot melt compositions were obtained according to the same
 manner as that described in Example 1 except for increasing the amount of
 the liquid softener to be mixed with 100 parts by weight of the styrene
 elastomer to 600 parts by weight, 800 parts by weight and 1000 parts by
 weight, respectively. The respective physical properties of the resulting
 compositions were determined and are shown in Table 2.
 As Comparative Examples, the respective physical properties were determined
 for the cases in which the procedure in Comparative Example 1 was repeated
 except that the amount of the liquid softener was changed in the same
 manner as above. The results are also shown in Table 2.
 &lt;Examples 7 to 9 and Comparative Examples 6 to 8&gt;
 As Examples, hot melt compositions were obtained according to the same
 manner as that described in Example 1 except for increasing the amount of
 the liquid softener to be mixed with 100 parts by weight of the styrene
 elastomer to 1500 parts by weight, 2000 parts by weight and 3000 parts by
 weight, respectively. The respective physical properties of the resulting
 compositions were determined and are shown in Table 3.
 As Comparative Examples, the respective physical properties were determined
 for the cases in which the procedure in Comparative Example 1 was repeated
 except that the amount of the liquid softener was changed in the same
 manner as above. The results are also shown in Table 3.
 &lt;Example 10 and Comparative Example 9&gt;
 According to the same manner as that described in Example 1 except for
 mixing an elastomer mixture having [.eta.] of 1.08, which is obtained by
 mixing 50 parts by weight of Elastomer a having [.eta.] of 1.46 with 50
 parts by weight of a carboxyl-modified styrene thermoplastic elastomer
 (referred to as Elastomer d) having [.eta.] of 0.67, with 700 parts by
 weight of a liquid softener, a hot melt composition was obtained. The
 respective physical properties of the resulting composition were
 determined and are shown in Table 4.
 As Comparative Examples, the respective physical properties were determined
 for the cases in which Elastomer c as above was mixed with 700 parts by
 weight of a liquid softener. The results are also shown in Table 4.
 The adhesion to an iron plate was determined in the following manner. A hot
 melt composition was bead-applied from a hand gun at 200.degree. C. on an
 iron plate having a width of 25 mm in a coating thickness of 3 mm and a
 coating width of 6 mm. After cooling to 20.degree. C., the bead was peeled
 off by hand and the adhesion was evaluated by scores .circleincircle. and
 .smallcircle..
 As is apparent from Table 4, it was confirmed that the compositions of the
 invention were superior in adhesion to the iron plate as described in
 Examples above, exhibited small compressive permanent strain and were
 superior in sealing characteristics. To the contrary, the compositions of
 the Comparative Examples were superior in adhesion to the iron plate, but
 exhibited large compressive permanent strain and were inferior in sealing
 characteristics.
 Although not shown in Tables, all the hot melt compositions obtained in
 Examples were superior in easy release property from the adherend.
 TABLE 1