JP5459438B1 - Network structure with excellent thermal dimensional stability - Google Patents

Abstract

An object of the present invention is to provide a network structure having excellent thermal dimensional stability and productivity and having a high hardness retention after a 40 ° C. compression residual strain test.
A three-dimensional random structure in which a continuous linear body made of a polyolefin-based thermoplastic elastomer having a fiber diameter of 0.1 mm to 3.0 mm is twisted to form a random loop, and the respective loops are brought into contact with each other in a molten state. A network structure having a loop bonded structure, an apparent density of 0.005 g / cm ^{3 to} 0.20 g / cm ³ , and a 40 ° C. compression residual strain of 5% to 15%.
[Selection figure] None

Description

  The present invention is an office chair, furniture, sofa, bed pad, mattress, train, automobile, two-wheeled vehicle, stroller, child seat, and other vehicles that are excellent in dry heat shrinkage and heat resistance and hardly change in dimensions even after washing and drying. The present invention relates to a net-like structure suitable for a seat, a floor mat, a shock-absorbing mat such as a collision or pinching member, and the like.

Currently, foam-crosslinked urethane is widely used as a cushioning material used for furniture, bedding such as beds, and seats for vehicles such as trains and automobiles.
Foam-crosslinked urethane has good durability as a cushioning material, but is inferior in moisture permeability and breathability and has a problem of being easily steamed due to heat storage. Furthermore, because it is not thermoplastic, it is difficult to recycle, and as a result, problems such as increased damage to the incinerator when incinerated and cost for removing toxic gas generated during incineration have been pointed out. . Therefore, landfill disposal is increased, but there is a problem that the landfill site is limited and the cost is increased because it is difficult to stabilize the ground of the landfill. Further, various problems have been pointed out, such as pollution problems of chemicals used during production, residual chemicals after foaming, and odors associated therewith, although the processability is excellent.

  In addition to the above-mentioned problems, using a bed pad or bed mat made of polyurethane material has excellent cushioning performance but poor breathability, and if you keep sleeping in the same posture for a long time, you may suffer from pressure ulcers etc. There is. In addition, it is difficult to wash when it becomes dirty, and it tends to cause hygiene problems.

  Patent Document 1 and Patent Document 2 disclose a network structure. This can solve various problems derived from the above-mentioned foam-crosslinked urethane, and is excellent in cushion performance and air permeability. However, the thermal dimensional stability is poor and has been a problem.

  Patent Document 3 discloses a method for producing a polyolefin-based network structure having low resilience and good sitting comfort and sleeping comfort. However, due to the relatively low melting point polymer characteristic of polyolefin-based, the 40 ° C. compression residual strain is about 20%, which is poor in heat resistance, and there is a problem that it is easy to get out when the outside air temperature becomes high such as in summer. there were. Against this background, demand for improvement of 40 ° C. compression residual strain has been increasing in the market.

  Patent Document 4 discloses a method for producing a network structure having excellent thermal dimensional stability. This can improve the good melt flow properties and heat resistance because it is crosslinked in water or in post-treatment water treatment. However, since the degree of crosslinking is as high as 65% or more, a network structure is required. In terms of productivity, such as the fact that it becomes harder than that, there are problems in terms of recycling like urethane, the cost of raw materials increases due to the copolymerization of relatively special monomers during polymerization, and the crosslinking process takes a week. There are various problems such as problems.

JP 7-68061 A JP 2004-244740 A JP 2006-200118 A JP 2013-181117 A

  The present invention has been made against the background of the problems of the prior art described above, and it is an object to provide a network structure that is excellent in thermal dimensional stability and productivity and has a small hardness change before and after the 40 ° C. compression residual strain test. To do.

As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention is as follows.
1. A three-dimensional random loop joined structure in which a continuous linear body made of a polyolefin-based thermoplastic elastomer having a fiber diameter of 0.1 mm to 3.0 mm is twisted to form a random loop, and the respective loops are brought into contact with each other in a molten state. A network structure having an apparent density of 0.005 g / cm ^{3 to} 0.20 g / cm ³ and a 40 ° C. compressive residual strain of 5% to 15%.
2. 2. The network structure according to 1 above, wherein the thickness of the network structure is 10 mm to 200 mm, and the hardness retention at 25% compression after the 40 ° C. compression residual strain test is 60% or more.

  The network structure according to the present invention has a small 40 ° C. compressive residual strain, excellent thermal dimensional stability, and a large hardness retention after the 40 ° C. compressive residual strain test, that is, a small change in hardness before and after the 40 ° C. compressive residual strain test. It is a network structure. With this excellent thermal dimensional stability and hardness retention rate, office chairs, furniture, sofas, bed pads, mattresses, train seats for cars such as trains, automobiles, motorcycles, strollers, and child seats, floor mats, and members for preventing collision and pinching Thus, it is possible to provide a net-like structure suitable for a cushion material used for a shock absorbing mat or the like. In particular, it has become possible to provide a net-like structure suitable for cushioning materials such as office chairs, furniture, sofas, bed pads, mattresses, etc., which are prone to heat up due to summer or body temperature.

  Hereinafter, the present invention will be described in detail.

  The network structure of the present invention uses a continuous linear body made of a polyolefin-based thermoplastic elastomer, so that the rubber elasticity of the material and the entire three-dimensional structure are integrated, and the effect of the pseudo-crystallization treatment described later is achieved. High durability and heat resistance are realized by applying. Furthermore, by relaxing the fiber diameter of an appropriate continuous linear body and the residual stress at the time of forming a network structure, durability in the thickness direction and thermal dimensional stability can be improved, and excellent heat resistance and durability can be realized. Moreover, since it becomes possible to regenerate by remelting, recycling becomes easy.

The polyolefin-based thermoplastic elastomer in the present invention is preferably a low-density polyethylene resin having a specific gravity of 0.94 g / cm ³ or less, particularly an ethylene / α-olefin copolymer comprising ethylene and an α-olefin having 3 or more carbon atoms. It is preferable to consist of resin. The ethylene / α-olefin copolymer of the present invention is preferably a copolymer described in JP-A-6-293131, and is formed by copolymerizing ethylene and an α-olefin having 3 or more carbon atoms. Is. Here, examples of the α-olefin having 3 or more carbon atoms include propylene, butene-1, pentene-1, hexene-1, 4-methyl-1-pentene, heptene-1, octene-1, nonene-1, and decene. -1, undecene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1, nonadecene-1, eicosene-1, etc., preferably butene -1, pentene-1, hexene-1, 4-methyl-1-pentene, heptene-1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1, tridecene-1, tetradecene-1 , Pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1, nonadecene-1, and eicosene-1. Two or more of these can also be used, and these α-olefins are usually copolymerized in an amount of 1 to 40% by weight. This copolymer can be obtained by copolymerizing ethylene and an α-olefin using a catalyst system having a specific metallocene compound and an organometallic compound as basic components.

If the specific gravity of the polyolefin-based thermoplastic elastomer exceeds 0.94 g / cm ³ , the network structure is likely to become hard, which is not preferable. The specific gravity is more preferably 0.935 g / cm ³ or less, and still more preferably 0.93 g / cm ³ or less. 0.8 g / cm ³ or more is preferred from the viewpoint of strength retention as the lower limit of the specific gravity, 0.85 g / cm ³ or more is more preferable.

  In addition, the melting point of the polyolefin-based thermoplastic elastomer of the present invention is preferably 80 ° C. or higher at which heat resistance can be maintained, and more preferably 85 ° C. or higher because the heat durability is improved. If necessary, two or more kinds of polymers polymerized by the above method, polybutadiene, polyisoprene, styrene-based thermoplastic elastomers such as styrene isoprene copolymers, styrene butadiene copolymers, and hydrogenated copolymers thereof. Of polymer modifiers can be blended. Furthermore, phthalate ester-based, trimellitic acid ester-based, fatty acid-based, epoxy-based, adipic acid ester-based, polyester-based plasticizers, known hindered phenol-based, sulfur-based, phosphorus-based, amine-based antioxidants, Reactions such as hindered amine, triazole, benzophenone, benzoate, nickel, salicyl and other light stabilizers, antistatic agents, peroxides and other molecular modifiers, epoxy compounds, isocyanate compounds, carbodiimide compounds, etc. Group-containing compounds, metal deactivators, organic and inorganic nucleating agents, neutralizing agents, antacids, antibacterial agents, fluorescent brighteners, fillers, flame retardants, flame retardant aids, organic and inorganic Of pigments can be added. It is also effective to increase the molecular weight of the thermoplastic resin in order to improve heat resistance and sag resistance.

  The component comprising the polyolefin-based thermoplastic elastomer constituting the network structure having excellent thermal dimensional stability according to the present invention has an endothermic peak at a melting point of 20 ° C. or higher and a melting point or lower in a melting curve measured with a differential scanning calorimeter. Is preferred. There may be two or more endothermic peaks below the melting point, and it may appear as a shoulder depending on the proximity to the melting point and the baseline shape. Those having an endothermic peak below the melting point have significantly improved heat sag resistance compared to those having no endothermic peak. The annealing treatment is not limited as long as the sample can be heat-treated at a temperature lower by at least 5 ° C. than the melting point, but the heat distortion resistance is further improved by applying compressive strain. An endothermic peak is more clearly expressed in a melting curve measured with a differential scanning calorimeter at a temperature not lower than the room temperature and not higher than the melting point of the cushion layer subjected to such treatment. In the case where annealing is not performed, an endothermic peak is not clearly expressed in the melting curve from room temperature to the melting point. The exact mechanism is not known, but by analogy with this, it is considered that the heat-stable resistance is improved by forming a metastable intermediate phase in which the hard segments are rearranged by annealing ( Hereinafter, this treatment is referred to as pseudo-crystallization treatment).

  In the network structure of the present invention, a continuous linear body made of a polyolefin-based thermoplastic elastomer having a fiber diameter of 0.1 mm to 3.0 mm is twisted to form a random loop, and the respective loops are brought into contact with each other in a molten state. 3D random loop joint structure. The fiber diameter is an important factor for obtaining a soft tactile sensation. If the fiber diameter is small, the hardness required for cushioning cannot be maintained. Conversely, if the fiber diameter is too large, the fiber becomes too hard. Must be set to a range. If the fiber diameter is less than 0.1 mm, the fiber will be too thin and the denseness and soft touch will be sufficient, but it will be difficult to ensure the required hardness. On the other hand, if the fiber diameter exceeds 3.0 mm, it is easy to ensure the required hardness, but the feeling of firmness becomes remarkable. A preferable fiber diameter is 0.2 mm to 2.5 mm.

The apparent density of the network structure of the present invention is an important factor that determines cushioning properties, is designed according to the application, and is 0.005 g / cm ^{3 to} 0.20 g / cm ³ , preferably 0.01 g / cm ³ ~0.18g / cm ^3, more preferably ^{0.02g / cm 3 ~0.15g / cm 3} . Apparent density is not maintained when the hardness required for 0.005 g / cm ³ less than the cushioning properties become too hard exceeds 0.20 g / cm ^3.

  In the present invention, 40 ° C. compressive residual strain means that the network structure is cut into a size of 10 cm × 10 cm, the thickness is measured (thickness before treatment: a), and the compressed state is 40% with respect to this thickness. After being left in the environment for 22 hours, the compressed state is released, and cooling is performed at room temperature for 30 minutes, and the thickness is measured again (post-treatment thickness: b). 100. It can be said that the smaller this value is, the less likely the thickness will decrease even when used in summer or in a relatively warm environment. That is, it can be said that it is an index of thickness change (sagging) when used in a warm environment.

  On the other hand, the 25% compression hardness retention after the 40 ° C. compression residual strain test is calculated by measuring the 25% compression hardness before and after the above measurement and calculating the hardness retention after the test. That is, it can be said that the 25% compression hardness retention after the 40 ° C. compression residual strain test is an index that is used in a warm environment and simply represents a change in sitting comfort when a thickness change occurs. .

  The network structure of the present invention has a 40 ° C. compression residual strain of 5% to 15%, preferably 5% to 14%, more preferably 6% to 13%, and even more preferably 7% to 12%. %, And most preferably 8% to 10%. When the 40 ° C. compressive residual strain exceeds 15%, the desired properties as a network structure excellent in dimensional stability are not satisfied. In order to obtain a network structure having a compression residual strain of less than 5% at 40 ° C., the method of the present invention is insufficient, and it is necessary to use severe processing conditions such as increasing the crosslinking density. From the viewpoint of melt fluidity, it is not preferable because it deviates from the gist of the present invention.

  The network structure of the present invention has a 25% compression hardness retention after a 40 ° C. compression residual strain test of preferably 60% or more, more preferably 63% or more, still more preferably 65% or more, and most preferably 70% or more. If the hardness retention at 25% compression after the 40 ° C. compression residual strain test is less than 60%, the hardness changes in use in a relatively hot environment, which is not preferable. The upper limit of the 25% compression hardness retention after the 40 ° C. compression residual strain test is not particularly limited, but is preferably 100% or less.

  The thickness of the network structure of the present invention is greatly related to cushioning properties, and is 10 mm to 200 mm, preferably 20 mm to 120 mm. If the thickness is less than 10 mm, the feeling of bottoming is too thin, and if it exceeds 200 mm, the cushion material is too thick and the comfort is impaired.

  The network structure of the present invention includes a multilayer structure. For example, the surface and the lower layer can be composed of linear bodies having different fiber diameters. For example, the surface layer is soft with a linear body with a small fiber diameter, while the lower layer is made of a linear body with a large fiber diameter to give hardness, so that both a soft tactile sensation and a feeling of bottoming can be reduced. Is also a preferred embodiment. Examples of the multi-layered method include a method of stacking network structures and fixing them on the side ground, a method of melting and fixing by heating, a method of bonding with an adhesive, a method of restraining with sewing or a band, and the like.

  By making the linear body constituting the network structure of the present invention a composite linear body, it is possible to impart a thermal bonding fiber function and increase the bonding strength between the linear bodies in contact. For example, by using the same material with different melting points, arranging a low melting point component in the sheath component and a high melting point component in the core component, and discharging and cooling, the bonding force between the linear bodies can be stronger than that of the single component Therefore, it can be said to be a preferred embodiment.

  The cross-sectional shape of the linear body constituting the network structure of the present invention is not particularly limited. However, a preferable anti-compression property and touch can be imparted by forming a hollow cross-section, an atypical cross-section, or a hollow atypical cross-section combining them. it can. The compressibility can be adjusted by adjusting the fiber diameter and the modulus of the material used, and the fiber diameter can be reduced by using a soft material. I can do it. A material having a slightly high modulus imparts a suitable anti-compressibility by lowering the hollowness and the degree of profile or reducing the fiber diameter. As another effect of the hollow cross section and the irregular cross section, when the hollow ratio and the irregularity degree are increased, when the same anti-compression property is imparted, the weight can be reduced, which is a preferable embodiment.

  An example of the production method of the present invention will be described. A three-dimensional network structure can be obtained by a known method described in JP-A-7-68061. For example, the thermoplastic elastomer is distributed to the nozzle orifice from a multi-row nozzle having a plurality of orifices, and is discharged downward from the nozzle at a melting temperature that is 20 ° C. or more higher than the melting point of the thermoplastic elastomer and less than 120 ° C., In a molten state, they are brought into contact with each other and fused to form a three-dimensional structure. After being sandwiched by a take-up net installed in the take-up device and cooled by a cooling tank, the product is drawn from the cooling tank by being sandwiched by a nip roller and drained. And drying to obtain a three-dimensional network structure smoothed on both sides or one side. In the case of smoothing only one surface, it is preferable to discharge it on an inclined take-up net and cool it while relaxing the form of only the take-up net surface while forming a three-dimensional structure by bringing them into contact with each other in a molten state.

As a method for obtaining a network structure excellent in thermal dimensional stability of the present invention, a speed difference is generated between a take-up net and a nip roller installed thereafter to relieve stress during molding. This speed difference can be realized by reducing the speed of the nip roller or by a mechanism that relieves stress behind the conveyor net, and is shown as a speed ratio. The speed ratio is calculated by the following formula.
Speed ratio (%) = (1−nip roller speed / take-off net speed) × 100

  The speed ratio is preferably 1.0% or more, more preferably 1.5% or more, and further preferably 2.0% or more. If the speed ratio between the take-off net and the nip roller is significantly higher than the level at which the residual distortion is eliminated, it is difficult to take the network structure straight, which is not preferable, and is preferably 20% or less, more preferably 15% or less. preferable.

  The mechanism by which the thermal dimensional stability is improved by increasing the speed ratio is not fully understood, but is considered as follows. If a net-like structure is created without removing residual distortion by pulling the net-like structure with a conveyor roll, the loop distortion will not be eliminated and it will be fixed in a relatively unstable state and compressed for a long time. It is considered that the spring effect of the loop is reduced and the thickness is difficult to return. On the other hand, if the network structure is created so as to remove the residual strain, it is considered that the loop shape is fixed in a relatively stable state and the spring effect by the loop can be exhibited. By stabilizing this loop, it is considered that the 25% hardness retention after the 40 ° C. compression residual strain test is also improved.

  Another method for obtaining a network structure excellent in thermal dimensional stability of the present invention is to increase the drying temperature after draining. The drying temperature is preferably 60 ° C or higher, more preferably 70 ° C or higher, and further preferably 80 ° C or higher. The drying temperature is preferably equal to or lower than the melting point of the polyolefin-based thermoplastic elastomer, and more preferably 10 ° C. lower than the melting point. The drying time is preferably 1 minute or longer, more preferably 10 minutes or longer, further preferably 20 minutes or longer, and most preferably 30 minutes or longer.

  Other methods for obtaining a network structure having excellent thermal dimensional stability according to the present invention include organic peroxides, organic peroxides and crosslinking aids as long as thermoplasticity and product recyclability are not impaired. A method of improving the inherent heat resistance of the polymer by using a combination of an agent, crosslinking with an electron beam, UV, or the like is also included. In the case of using a peroxide cross-linking agent, it can be cross-linked under melting conditions or in a subsequent drying step by adding a peroxide cross-linking agent at the time of melting. Electron beam crosslinking can be crosslinked by irradiating an electron beam in a nitrogen atmosphere or in the presence of oxygen after molding a network structure. In the case of UV cross-linking, each cross-linking agent is added at the time of melting, and after forming a network, it can be cross-linked by irradiating with UV.

  In the case of crosslinking, the gel fraction is preferably 50% or less from the viewpoint of ensuring melt fluidity during spinning and recyclability. The gel fraction is calculated by Soxhlet extraction of the network structure using xylene as a solvent and dividing the remaining solid weight by the original weight.

  In order to achieve the above gel fraction, the amount of peroxide is preferably 500 ppm or more and 30000 ppm or less of the network structure. The electron beam irradiation amount is preferably 120 kGy or less. Since the above range varies depending on the peroxide species used, polymer composition, network structure, crystallinity, etc., appropriate examination is necessary.

  In order to obtain a network structure excellent in thermal dimensional stability of the present invention, it is also a preferable method to combine the above methods as appropriate.

  When the linear body constituting the network structure is combined with a seascore structure and the aim is to improve the bonding strength by utilizing the melting point difference, the melting point difference of the thermoplastic resin used for the sheath component and the core component is 20 ° C. or more. It can be obtained by using a thermoplastic resin and distributing the seascore just before the orifice. More preferably, the difference in melting point between the thermoplastic resin used for the sheath component and the core component is 30 ° C. or more. The spinning temperature in the case where the linear body constituting the network structure is combined with the seascore structure is preferably at least 10 ° C. higher than the melting point of the low melting point component.

  In the case of making the cross-section of the linear body constituting the network structure, for example, in the case of a hollow cross-section, it is possible to use an orifice capable of forming a hollow orifice shape. If the hollow cross section has a large ballast effect, it is easy to increase the hollowness ratio.However, if the hollowness ratio is small, the hollowness ratio of the yarn cannot be increased unless the hollowness ratio of the orifice is increased as much as possible. Must be selected.

  When the obtained network structure is used as it is in a network state, it is drained and dried, cut into a desired size, and used.

  When the obtained network structure is formed by edging or various patterns by thermoforming, the thermoforming temperature is preferably 10 to 50 ° C. lower than the melting point of the polyolefin-based thermoplastic elastomer constituting the network structure. If the temperature is lower than the melting point of the thermoplastic elastomer by less than 10 ° C., the deformation of the structure may become too large, which is not preferable. If the temperature is lower than the melting point of the thermoplastic elastomer by more than 50 ° C., the outer thermoformed shape may not be sufficiently formed. In addition, it is preferable that the thermoforming is preheated and formed with a hot press mold. The remaining heat may be heated only on one side and the other side may be press-molded without heating. In this case, when the pressing pressure is increased by about 10%, a joining state equivalent to that formed by pressing the upper and lower heating molds can be obtained. The obtained thermoformed product is cut into a desired size by a method such as punching and used for various cushions.

  By heating at a temperature not higher than the melting point by hot press molding, the above-mentioned pseudo crystallization treatment effect can be imparted, so that it is not necessary to actively anneal before molding. The pseudo crystallization temperature is at least 10 ° C. lower than the melting point and 20 ° C. or higher. This treatment has an endothermic peak below the melting point, and the sag resistance is remarkably improved as compared with the case where the pseudo crystallization treatment is not performed (the case where no endothermic peak is provided).

  The network structure of the present invention is processed from a resin production process to a molded body within a range not deteriorating the performance, and at any stage of commercialization, deodorizing antibacterial, deodorizing, antifungal, coloring, aroma, flame retardant, moisture absorption and desorption Etc. can be imparted by processing such as drug addition.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, the measurement and evaluation of the characteristic value in an Example were performed as follows.

(1) Fiber diameter A sample is cut into a size of 20 cm × 20 cm, and a linear body is collected from about 10 mm from each of the surface layer and the inner layer of the net-like body. The surface layer fibers are collected from the outermost surface layer in the thickness direction of the mesh body, that is, from a position where no fibers are present outside the fibers, and the inner layer fibers are collected from within 30% of the thickness center value in the thickness direction of the mesh body. The fiber diameters of the linear bodies collected from 10 places are measured by focusing an optical microscope at a fiber diameter measurement place at an appropriate magnification. (Average value of n = 20)
(2) Sample thickness and apparent density The sample was cut into a size of 30 cm x 30 cm, left unloaded for 24 hours, and then measured at four heights with a FD-80N type thickness gauge manufactured by Kobunshi Keiki. The average value is taken as the sample thickness. The sample weight is measured by placing the sample on an electronic balance. Further, the volume is obtained from the sample thickness, and is represented by a value obtained by dividing the weight of the sample by the volume. (Each average value of n = 4)
(3) Melting point An endothermic peak (melting peak) temperature is determined from an endothermic curve measured at a temperature increase rate of 20 ° C./min using a differential scanning calorimeter Q200 manufactured by TA Instruments.
(4) 40 degreeC compression residual strain A sample is cut | disconnected to a magnitude | size of 10 cm x 10 cm, and the thickness (a) before a process is measured by the method as described in (2). The sample whose thickness is measured is sandwiched between jigs that can be held in a 50% compressed state, placed in a dryer set at 40 ° C., and left for 22 hours. Thereafter, the sample is taken out, cooled and the compression strain is removed to determine the thickness (b) after 30 minutes. From the thickness (a) before treatment, the formula {(a)-(b)} / (a) × 100 Calculate: Unit% (average value of n = 3).
(5) Hardness at 25% compression After cutting a sample into a size of 30 cm x 30 cm and leaving it in an environment of 20 ° C ± 2 ° C under no load for 24 hours, Orientec in an environment of 20 ° C ± 2 ° C Using a pressure plate having a diameter of 200 mm and a thickness of 3 mm with a Tensilon manufactured by the company, compression of the center of the sample is started at a speed of 10 mm / min, and the thickness when the load reaches 5 N is measured to obtain the hardness meter thickness. The position of the pressure plate at this time is taken as the zero point, and after compression to 75% of the hardness meter thickness at a speed of 100 mm / min, the pressure plate is returned to the zero point at a speed of 100 mm / min. Subsequently, compression was performed at a speed of 100 mm / min to 25% of the thickness of the hardness meter, and the load at that time was defined as 25% compression hardness: unit N / φ200 (average value of n = 3).
(6) 25% hardness retention after 40 ° C. compression residual strain test A sample is cut into a size of 10 cm × 10 cm, and the thickness (a) before treatment is measured by the method described in (2). The sample whose thickness was measured was measured for the hardness at 25% compression by the method described in (5) to obtain the hardness (b) at 25% compression before treatment. The sample for which hardness measurement has been completed is sandwiched between jigs that can be held in a compressed state of 50% of the thickness of (a), placed in a dryer set at 40 ° C., and left for 22 hours. After 22 hours, the sample is removed, the compressed state is released, the sample is left unloaded, and left at room temperature for 30 minutes. After cooling for 30 minutes, the hardness at 25% compression is measured by the method described in (5), and the treated hardness is taken as 25% compression hardness (c). The 25% hardness retention after the 40 ° C. compression residual strain test is calculated by the following formula, which is obtained by dividing the 25% compression hardness after treatment by the 25% compression hardness before treatment.
(25% hardness retention after 40 ° C compression residual strain test)
= (C) / (b): Unit% (average value of n = 2)

[Example 1]
Polyolefin-based elastomers are polymerized by polymerizing hexane, hexene, and ethylene using a metallocene compound as a catalyst to form an ethylene / α-olefin copolymer, then adding 2% antioxidant, kneading, pelletizing, and thermoplasticity. Elastic resins A-1 and A-2 were obtained. The obtained thermoplastic elastic resin A-1 has a hexene copolymerization ratio of 2.9%, a specific gravity of 0.919, a melting point of 110 ° C., and the thermoplastic elastic resin A-2 has a hexene copolymerization ratio of 4.5%, The specific gravity was 0.906 and the melting point was 103 ° C. A thermoplastic elastic resin A-3 was obtained by mixing and kneading 1.5 parts by weight of perbutyl P-40MB (K) manufactured by NOF Corporation as a crosslinking agent to the thermoplastic elastic resin A-1.

In the nozzle effective surface of the width direction 1050mm, width direction width 50mm nozzle to the nozzle which made the orifice shape the outer diameter 2mm, the inner diameter 1.6mm, the orifice which made the triple bridge hollow formation cross section with the hole pitch 5mm staggered arrangement, The obtained thermoplastic elastomer (A-1) was discharged below the nozzle at a melting temperature of 210 ° C. at a discharge rate of 2.0 g / min per single hole, cooling water was placed under the nozzle surface 26 cm, and the width 150 cm. The stainless steel endless nets are arranged in parallel with an opening width of 40 mm apart so that a part of the pair of take-up conveyors comes out on the surface of the water, and the molten discharge line is twisted to form a loop to form a contact portion. A three-dimensional network structure is formed while fusing, and both sides of the molten network are sandwiched by a take-up conveyor and drawn into cooling water at a rate of 1.15 m / min. After both sides are flattened, they are taken out with a nip roller at a speed of 1.10 m / min, that is, with a speed ratio of 4.3%, cut into a predetermined size, dried and heat-treated with hot air at 70 ° C. for 20 minutes, and reticulated. A structure was obtained.
Table 1 shows the physical properties of the obtained network structure. The obtained network structure is formed of a continuous linear body having a hollow cross section, a hollow ratio of 28%, and a fiber diameter of 1.2 mm, an apparent density of 0.056 g / cm ³ , and a flat surface. A net-like structure having a thickness of 39 mm, a 40 ° C. compression residual strain of 11.8%, a 25% compression hardness of 250 N / φ200, and a 25% hardness retention after a 40 ° C. compression residual strain test of 64.0%. It was a structure.

[Example 2]
A-1 is used as the thermoplastic elastomer, the spinning temperature is 220 ° C., the single hole discharge rate is 1.8 g / min, the nozzle surface-cooling water distance is 30 cm, the take-up speed is 1.26 m / min, and the nip roller is min / min. It was obtained in the same manner as in Example 1 except that it was taken up at a speed of 1.20 m, that is, a speed ratio of 4.8%, and the drying temperature was 80 ° C.
Table 1 shows the physical properties of the obtained network structure. The obtained network structure is formed of a linear body having a hollow cross section, a hollowness of 22%, a fiber diameter of 0.8 mm, an apparent density of 0.047 g / cm ³ , and a flattened surface. The thickness is 38 mm, the 40 ° C. compression residual strain is 10.2%, the 25% compression hardness is 198 N / φ200, the 25% compression hardness retention after the 40 ° C. compression residual strain test is 68.1%. It was a network structure.

[Example 3]
A-2 is used as a thermoplastic elastomer, spinning temperature is 210 ° C., single hole discharge is 1.5 g / min, nozzle surface-cooling water distance is 28 cm, take-up speed is 1.22 m / min, nip roller is min / min A network structure was obtained in the same manner as in Example 1 except that the sample was taken at a speed of 1.20 m, that is, a speed ratio of 1.6%, and the drying time was 30 minutes.
Table 1 shows the physical properties of the obtained network structure. The obtained network structure is formed of a linear body having a hollow cross section, a hollow ratio of 25%, a fiber diameter of 1.2 mm, an apparent density of 0.038 g / cm ³ , and a flattened surface. A network structure having a thickness of 40 mm, a 40 ° C. compression residual strain of 13.8%, a 25% compression hardness of 166 N / φ200, a 25% hardness retention after a 40 ° C. compression residual strain test of 62.5% It was a body.

[Example 4]
A-3 is used as a thermoplastic elastomer, spinning temperature is 230 ° C., single hole discharge is 1.5 g / min, nozzle surface-cooling water distance is 28 cm, take-up speed is 1.30 m / min, nip roller is min / min A network structure was obtained in the same manner as in Example 1 except that it was taken up at a speed of 1.26 m, that is, a speed ratio of 3.1%, and the drying temperature was 80 ° C.
Table 1 shows the physical properties of the obtained network structure. The obtained network structure is formed of a linear body having a hollow cross section, a hollow ratio of 24%, and a fiber diameter of 0.9 mm, an apparent density of 0.036 g / cm ³ , and a flat surface. The thickness is 40 mm, the compression residual strain at 40 ° C. is 7.1%, the hardness at 25% compression is 180 N / φ200, and the hardness retention at 25% compression after the 40 ° C. compression residual strain test is 75.1%. It was a network structure.

[Comparative Example 1]
A network structure was obtained in the same manner as in Example 1 except that the take-up speed was 1.15 m / min and the nip roller was 1.15 m / min, that is, the speed ratio was 0.0%.
Table 1 shows the physical properties of the obtained network structure. The obtained network structure is formed of a linear body having a hollow cross section, a hollow ratio of 27%, a fiber diameter of 1.2 mm, an apparent density of 0.056 g / cm ³ , and a flat surface. The thickness is 39 mm, the 40 ° C. compression residual strain is 16.3%, the 25% compression hardness is 242 N / φ200, the 25% compression hardness retention after the 40 ° C. compression residual strain test is 54.4%. It was a network structure.

[Comparative Example 2]
A network structure was obtained in the same manner as in Example 3 except that the drying step was eliminated.
Table 1 shows the physical properties of the obtained network structure. The obtained network structure is formed of a linear body having a hollow cross section, a hollow ratio of 25%, a fiber diameter of 1.2 mm, an apparent density of 0.038 g / cm ³ , and a flattened surface. The thickness is 40 mm, the 40 ° C. compression residual strain is 22.2%, the 25% compression hardness is 155 N / φ200, the 25% compression hardness retention after the 40 ° C. compression residual strain test is 48.4%. It was a network structure.

  The present invention is an office chair, furniture, sofa, bed pad, mattress, electric train, automobile, and the like, which is excellent in thermal dimensional stability, which has been a problem in the past, without impairing the comfortable sitting comfort and breathability that have been conventionally provided A net-like structure suitable for vehicle seats such as motorcycles, strollers and child seats, floor mats and mats for shock absorption such as collision and pinching prevention members, etc. can be provided, greatly contributing to the industry.

Claims (2)

A three-dimensional random loop joined structure in which a continuous linear body made of a polyolefin-based thermoplastic elastomer having a fiber diameter of 0.1 mm to 3.0 mm is twisted to form a random loop, and the respective loops are brought into contact with each other in a molten state. A network structure having an apparent density of 0.005 g / cm ^{3 to} 0.20 g / cm ³ and a 40 ° C. compressive residual strain of 5% to 15%.   2. The network structure according to claim 1, wherein the network structure has a thickness of 10 mm to 200 mm and a 25% compression hardness retention after the 40 ° C. compression residual strain test is 60% or more.