JP2637269B2 - Hot melt adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a disposable diaper having a diaper surface or a sanitary napkin that requires a diaper cover. The present invention relates to a hot-melt adhesive composition for preventing slippage which is partially applied to the surface of a napkin.

[Conventional technology and its problems] Conventionally, a slip-preventing adhesive that is partially applied to the surface of a disposable diaper or a sanitary napkin (hereinafter referred to as a "napkin") has a slip-preventing effect and a texture due to tack force. From the viewpoint of maintaining softness, a hot melt adhesive obtained by using a synthetic rubber as a base polymer and adding a tackifying resin and a plasticizing oil thereto is used. Such hot melt adhesives are soft, white or colorless and odorless, and have excellent initial adhesion to diaper covers and shorts (hereinafter referred to as “underwear”) to be adhered to the cloth. It is required to have excellent properties from low to high temperatures and that no adhesive remains on the fabric side when removing the disposable diaper or napkin after use. However, there is no conventional hot melt adhesive that satisfies all of the above requirements. For example, a hot melt adhesive based on synthetic rubber, which has been a mainstream product in the past, contains a large amount of plasticizing oil with an emphasis on texture, but when using a napkin or the like, the ambient temperature depends on the body temperature. On the other hand, when the temperature rises from room temperature to high temperature, the low molecular weight material in the adhesive oozes out in a liquid state, and consequently has the drawback that the cloth such as underwear is soiled. Among the above synthetic rubbers, those based on styrene-ethylene-butylene-styrene block copolymer (SEBS) have been awarded because they do not relatively cause the above problems. That is,
SEBS has a much higher amount of plasticizing oil that can be incorporated into a polymer than other synthetic rubbers, such as styrene-isoprene-styrene block copolymer (SIS) and styrene-butadiene-styrene block copolymer (SBS). This is because the amount of oil that seeps out of the base polymer even when the temperature rises is small. However, even if the above SEBS is used as a base polymer, if used for a long time in a body temperature atmosphere, the hot melt adhesive gradually softens and sinks into the fiber composition of the underwear fabric to be bonded,
Since the apparent adhesive strength is greatly increased and the cohesive strength is decreased, the adhesive layer has a disadvantage that the adhesive layer undergoes cohesive failure when the napkin or the like is removed and the adhesive remains on the cloth. The most effective solution to this problem is to reduce the amount of the plasticizing oil.However, when the amount of the plasticizing oil is reduced, the initial adhesive strength is extremely reduced and, at the same time, the hot melt adhesive becomes hard. There is a problem that the napkin or the like tends to shift during use. Therefore, in practice, the amount of the plasticizing oil is adjusted in order to achieve the above balance. However, there is a limit to this, and a satisfactory result is not always obtained. Also,
Since the hot melt adhesive has tackiness at room temperature, care has been taken not to inadvertently attach the release paper to the adhesive application surface when not using a napkin or the like, but during storage, etc. There is a problem in that the release agent applied to the release paper migrates to the surface of the adhesive and the adhesive strength of the hot melt adhesive itself decreases. in this way,
In fact, conventional hot melt adhesives do not yet have satisfactory performance.

The present invention has been made in view of such circumstances,
Conventionally, it has not been compatible with both the anti-slipping effect and the fabric releasability at the same time, has a soft texture, and has virtually no tack at room temperature, so there is no need for release paper, which is conventionally required, and near body temperature It is an object of the present invention to provide a hot melt adhesive composition which produces a high tack force at the above temperature.

[Means for solving the problem]

In order to achieve the above object, the hot melt adhesive composition of the present invention contains 15 to 65% by weight of an α-olefin resin.
25-65% by weight of hydrogenated tackifying resin contained
The styrene-ethylene-propylene-styrene block copolymer is contained in an amount of 5 to 25% by weight, and the plasticizing oil is contained in an amount of 3 to 15% by weight.

[Action]

That is, the inventor of the present invention has sought to obtain an adhesive composition which simultaneously satisfies both the conventional anti-slipping effect and the fabric releasability, and has a low tack force at room temperature and a high tack force near body temperature. The research was repeated. In the course of this research, the present inventor focused on the property of α-olefin-based resin, which has adhesiveness during melting, but hardens in a few seconds upon cooling, and mixes it with the synthetic rubber, which has tackiness at room temperature. Then I came up with the idea that a good effect could be obtained. Based on this idea, the research was repeated and the technical common sense that the α-olefin-based resin lacked compatibility with synthetic rubber was broken, and the α-olefin-based resin was synthesized with the α-olefin-based resin as a base polymer of the hot melt adhesive composition. A mixture with a rubber, styrene-ethylene-propylene-styrene block copolymer (SEPS), was used. As a result, they have found that excellent effects can be obtained and the amount of plasticizing oil can be reduced. And as a result of further study, the mutual ratio of the above SEPS was set to the above specific range, and a hydrogenated tackifying resin and a plasticizing oil were blended in a predetermined amount, and the slip preventing effect and the fabric release property were improved. It has been found that a hot-melt adhesive can be obtained at low temperature at room temperature and a high tack force is generated near body temperature (there is no need for release paper), and the present invention has been achieved.

In addition, the said normal temperature means about 20 degreeC, and the vicinity of body temperature means the range of about 35-40 degreeC.

 Next, the present invention will be described in detail.

The hot melt adhesive composition of the present invention contains an α-olefin-based resin and SEPS as base polymers, a tackifying resin, and a plasticizing oil, respectively, in predetermined proportions.

The α-olefin-based resin preferably contains at least 40% by weight (hereinafter abbreviated as “%”), preferably 45 to 65% of polypropylene, and has a crystallinity of 5 to 30%. The softening point is not particularly limited. If the amount of the α-olefin-based resin is too large, the initial adhesive strength is reduced, and if the amount is too small, blocking due to tacking force occurs and release paper is required, so that the amount used is 15% of the entire hot melt adhesive composition. Must be set to ~ 65%. Preferred is in the range of 25-50%.

The above SEPS is a copolymer composed of a mixture of an ethylene structure and a propylene structure in the middle of the styrene polymer blocks at both ends. For example, a styrene-polymer having an isoprene polymer block between the styrene polymer blocks at both ends is provided.
It can be easily obtained by hydrogenating the isoprene polymer portion of the isoprene-styrene block copolymer. The SEPS has a two-phase structure in which a styrene phase as a hard segment and an ethylene-propylene phase as a soft segment function. This SEPS
However, contrary to conventional technical common sense, synthetic rubber and α-olefin-based resin are incompatible with each other,
The above-mentioned ethylene-propylene phase has a chemical structure
-It is considered to have the same skeleton as the olefin-based resin. In addition, as described above, SEPS has a good oil retaining property, and does not seep out of the plasticized oil over time,
In addition, a high initial adhesive strength and a stable adhesive strength from a normal temperature to a body temperature range can be obtained, and at the same time, a soft texture can be given to the hot melt adhesive layer. However, the above-mentioned
SEPS having a styrene content of 10 to 35% is preferable. If the styrene content is less than 10%, the tacking force becomes too strong, and if it exceeds 35%, the adhesive strength required for preventing slippage cannot be obtained. It is necessary to set the amount of the SEPS to 5 to 25% based on the whole composition. Preferred is 7-15%. If the amount of SEPS is less than 5%, the adhesion is poor, and conversely 25%
If the amount is too large, the tacking force becomes too strong.

The tackifier resin generally has a lower molecular weight than the base polymer, and improves the wettability of the composition and at the same time imparts the initial adhesive strength, lowers the viscosity of the entire composition, and reduces the viscosity of the adhesive. This is to improve coating workability. Such a resin is desirably colorless or white and odorless even when heated at room temperature. From these facts, in the present invention, in particular, hydrogenated resins (hereinafter abbreviated as "hydrogenated resins"), such as hydrogenated aromatic petroleum resins, hydrogenated aliphatic petroleum resins, hydrogenated resins The used terpene resin is used. That is, as described above, the hydrogenated product is the α-olefin-based resin and
Since the compatibility with SEPS is improved, an adhesive composition using the same is provided with a wide range of adhesive properties from low to high temperatures, and at the same time, the hydrogenated resin has a double bond due to its chemical structure. As a result, excellent thermal stability is also provided. The softening temperature of the hydrogenated resin is not particularly limited, and it may be a solid or a liquid at normal temperature. However, a liquid is preferred because it has an effect as a plasticizer. The amount of such a tackifier resin is 25 to 65% of the entire composition.
%, Preferably 35-55%. If the amount is more than 65%, the texture becomes hard and the room-temperature adhesiveness becomes extremely poor. If the amount is less than 25%, the wettability to the adherend decreases and the initial adhesive strength deteriorates. .

Further, the plasticizing oil used in the present invention may be any plasticizing oil as long as it is used in a usual hot melt adhesive composition. However, those having a lower molecular weight than the above tackifying resin, which serve as a viscosity modifier for the composition, improve low-temperature tackiness, and make the composition flexible are preferred. As such a plasticized oil, an oil obtained by mixing three components of a paraffin-based component, a naphthene-based component, and an aromatic-based component is generally used. In such a mixed oil, when the amount of the paraffin-based component is increased, the thermal stability of the obtained composition is improved, and when the amount of the naphthene-based component is increased, the low-temperature adhesion is improved. The compounding amount of such a plasticizing oil is 3 to
It is set to 15%, preferably 3 to 10%. The amount is 3
If the amount is less than 15%, the hand becomes hard and the low-temperature adhesiveness decreases, and if it exceeds 15%, the high-temperature adhesiveness decreases.

The hot melt adhesive composition of the present invention may be appropriately selected and blended with various additives used in conventional hot melt adhesive compositions in addition to the above essential components.
Such additives include, for example, antioxidants, stabilizers, fillers, pigments, ultraviolet absorbers and the like from the viewpoint of economy and practical use. Also, various thermoplastic polymer compounds can be used.

The hot melt adhesive composition of the present invention can be obtained, for example, by placing the above-mentioned raw materials in a melt-stirring / mixing vessel and mixing under heating.

Next, examples of the present invention will be described together with comparative examples.

[Examples 1 to 13] The raw materials shown in Table 1 below were blended according to the following composition, and were melted and kneaded at about 150 ° C to obtain a desired hot melt adhesive composition.

Next, the characteristics of the products of the above examples were measured by the following methods, and the results are shown in Table 2 below.

<Initial adhesive strength> In a 25 ° C atmosphere, a hot melt adhesive composition applied to a thickness of 50 μm on a PET film and each piece of shorts were bonded together over a width of 2.54 cm x length of 20 cm. A load was applied and left for 1 hour. Thereafter, the peel strength was measured using a tensile tester (based on JIS Z 0237).

<Adhesive Force with Time> A test piece produced in the same manner as in the measurement of the initial adhesive force was left for 8 hours under a 40 ° C. atmosphere with a load of 1 kg. Thereafter, the peel strength was measured using a tensile tester (based on JIS Z 0237).

<Removability of adhesive from the adhesive> Observed the peeled surface of the peeled shorts after performing the above-mentioned adhesive measurement with time, を indicates that the hot melt adhesive composition did not remain at all, and △,
The case where all remained was evaluated as x.

<Slip prevention force> A sanitary napkin coated with a hot melt adhesive was spread flat and left in a thermostat at 30 ° C for 2 hours. Furthermore, a piece of cotton cloth (80 mm x 200 mm) was stuck on a glass plate of an adhesive strength tester adjusted to 30 ° C, the release paper of the above sample was peeled off, and the side with the hot melt adhesive was facing down, and was flattened on the piece of cotton cloth. , And the tab on the pulling side was sandwiched between the pulling clips. Next, 750 g of a hanging pendant was attached to the approximate center of the sample and attached for 1 minute. One minute later, instead of removing the hanging pliers for attachment, 225 g of the hanging hangers were placed on the sample, and a pulling load of 230 g was immediately applied to the laces to pull. If it does not shift within 1 minute, change the pull load to 250 g and pull. Then, when there is no deviation within 1 minute, the tension is further increased by 20 g and the tension is continued. In these measured values, those having an average of 300 g or more and a minimum of 250 g or more were evaluated as ○, and those less than 250 g were evaluated as ×. The number of samples was set to 10 <Compliant with the measurement method described in the application for approval of the manufacture (import) of sanitary treatment products issued by the Japan Sanitary Manufacturers Association>.

<Tack Force> A 50 μm polyester film was coated with 50 μm of a hot melt adhesive and cut into a 25 mm × 125 mm test sample to form a loop with the adhesive surface outside.
This sample was adhered to an adherend (polyethylene plate) having a width of 25 mm at 300 mm / min, and the force when pulled up at the same speed as above was measured. In this example, one hour after application, the one in a 20 ° C temperature atmosphere was cured at 40 ° C for 15 minutes,
(Near body temperature) Two kinds of measurements were performed. The number of samples was five and the average was the measured value.

<Thermal stability> Viscosity reduction rate The above example was left for 72 hours in a temperature atmosphere of 180 ° C., and the viscosity before and after that was measured to calculate the viscosity reduction rate, which was used as an index of thermal stability. The calculation formula is as follows.

V: 16 degrees of hot melt adhesive composition left at 180 ° C. for 72 hours
Melt viscosity at 0 ° C. Vo: 160 of hot melt adhesive composition before subject to thermal history
Melt viscosity at 0 ° C. Hue The hue of the hot melt adhesive composition left in an atmosphere at 180 ° C. for 72 hours was visually determined. ◎ indicates completely colorless or white, ○ indicates almost colorless or almost white, 、 indicates slightly colored, and X indicates clearly colored.

Odor The odor of the hot melt adhesive composition which had been given a heat cover in the same manner as in the observation of the above hue was evaluated by a sensory test (10 panelists). ◎: completely odorless, ○: almost odorless, Δ: slight odor, X: obvious odor

[Comparative Examples 1 to 14] In addition, 14 types of comparative examples having different composition from the above-mentioned example were produced. These compositions are shown in Table 3 below.
The characteristics of each of the comparative examples were evaluated in the same manner as in the example. The results are shown in Table 4 below.

From the results in Table 4 above, the product of Comparative Example shows unfavorable characteristics in any of the items of adhesiveness, fabric releasability, displacement prevention power, and thermal stability (hue, odor). Also,
Some of them have high tack force at room temperature (20 ° C.). On the other hand, as shown in the results of Table 2 above, it can be seen that the products of Examples show excellent characteristics in all items. At room temperature, the tack force is low, but at 40 ° C., the tack force is high.

〔The invention's effect〕

As described above, the hot melt adhesive composition of the present invention is a special composition in which an α-olefin resin and SEPS are mixed at a specific ratio, and a hydrogenated tackifying resin and a plasticizing oil are added thereto at a specific ratio. Is a base polymer. Therefore, it has excellent initial adhesiveness, and when it is partially applied to the surface of a napkin or the like and used as a slip stopper, the napkin or the like is not temporarily fixed with an appropriate strength to the cloth for shorts or the like. Nothing. Further, since the composition of the present invention is also excellent in fabric releasability, the adhesive does not remain on the fabric side when the napkin or the like is removed after use. Also,
No exudation of plasticizing oil. Further, since a hydrogenated resin is used as the tackifying resin, the resin is excellent in thermal stability, and there is no fear of coloring or generating odor even when heated in a process of manufacturing a napkin or the like. In particular, since the composition of the present invention uses the special compound as described above as a base polymer, it has low tack at room temperature and lacks adhesion, but has high tack at around body temperature. Demonstrate high adhesion. For this reason, in a napkin or the like to which this is applied, it is not necessary to cover the adhesive-applied portion with release paper as in the related art, and the cost can be reduced. The napkin or the like exerts a strong adhesive force when the temperature of the adhesive-applied portion rises to near the body temperature due to use, and firmly adheres to the shorts or the like, and exhibits a slip-preventing effect. Therefore, the hot melt adhesive composition of the present invention is most suitable as an adhesive for preventing slippage of a napkin or the like.

Claims (1)

(57) [Claims] An α-olefin resin is contained in an amount of 15 to 65% by weight, a hydrogenated tackifier resin is contained in an amount of 25 to 65% by weight, and a styrene-ethylene-propylene-styrene block copolymer is contained in an amount of 5 to 25%. A hot melt adhesive composition characterized in that the hot melt adhesive composition contains 3 to 15% by weight of a plasticizing oil.