KR20100110448A - A low-density polyolefin foam with cell gradient using electrobeam crosslinkage technique - Google Patents

Abstract

PURPOSE: A low-density polyolefin foamed body is provided to secure the fire retardant property, the profitability, and the environment-friendly property by inducing the cell gradient of the foamed body. CONSTITUTION: A fire retardant low-density polyolefin foamed body contains the following: 100 parts of resin by weight containing recycled low-density polyethylene and a recycled ethylene vinylacetate copolymer in a weight ratio of 8:2~6:4; 2~5 parts of cross-linking agent by weight; 10~15 parts of blowing agent by weight; 0~2 parts of blowing aid by weight; 0~2.5 parts of internal release agent by weight; 0~5 parts of external release agent by weight; 0~10 parts of plasticizer by weight; 0~2.5 parts of heat transfer accelerator by weight; 0~2.5 parts of additive by weight; and 150~250 parts of flame retardant by weight.

Description

Low density polyolefin foam with cell gradient using electron beam crosslinking technology {A LOW-DENSITY POLYOLEFIN FOAM WITH CELL GRADIENT USING ELECTROBEAM CROSSLINKAGE TECHNIQUE}

The present invention relates to low density polyolefin (particularly polyethylene) foams having a cell gradient using an E-beam crosslinking technique and a method of manufacturing the same. More specifically, the present invention relates to flame retardant low density polyolefin nanofoams prepared by electron beam crosslinking. In addition, the present invention has a limiting oxygen index (LOI) of 28 or more, prepared by diversifying the electron beam irradiation method to induce a cell gradient of the foam, thereby preventing the spread of flame in the outer portion of the foam having a small cell size, carbonization of 28 or more, Flame retardant polyolefin nanofoams with a char yield of about 45-55%, CO gas generation of about 0.11 kg / kg, smoke density (light transmittance in smoke) of 97% or more, and UL-94 grade VO. It is about.

Conventional polyolefin foam has a certain degree of flame retardancy is secured, but other physical properties are not good, especially it is difficult to be seen as an environmentally friendly material, there was a lot of room for improvement. In particular, in the case of chemical crosslinking, the surface of the foam and the characteristics of the cell are not uniform, and it is not easy to control the size of the cell according to the size of the cell and the cross section (depth) of the foam. However, the foam by electron beam crosslinking has excellent surface characteristics and can give a cell gradient according to electron beam irradiation conditions. In addition, this technology can respond to environmental regulations (RHoS) due to the use of non-halogen-based flame retardants by using inorganic flame retardants in olefin resins. It is a manufacturing technique of a foam.

At the same time, as economies, safety and economics have been secured due to the loss of competitiveness due to the rapid decline in added value under the infinite competition due to the difficulty of the foaming industry and the diversification of similar materials, the economic Although the necessity arises, most of the related industries do not satisfy this due to lack of research base and technology as most small and medium-sized enterprises. Most producers mainly produce non-crosslinked products using expensive pure raw materials and expensive processing equipment. The sharp decline in added value and the resulting loss of competitiveness.

In particular, intermolecular crosslinking is a very important process for maintaining the mechanical properties of the product due to the ease of flame retardation and carbonization of the polymer foam, and it also reduces the damage to life and property, which is the most important part of flame retardancy, while responding to the use of halogen flame retardants. It is essential to block flame propagation and minimize the release of toxic gases in the possible direction.

As part of the measures to solve the above problems, the present inventors induce the chemical cross-linking and optical cross-linking through the recycling of recycled plastics, in particular, the application of recycled polyethylene, as well as improving the eco-friendliness, safety, mechanical properties more economical And a flame retardant polyolefin crosslinked foam composition which can be manufactured into a product having excellent flame retardancy, and which can be very usefully used as an economic product by recycling waste resins (see Korean Patent No. 772289). Korean Patent Publication No. 772289 discloses "30-50% by weight of polypropylene, 30-50% by weight of recycled polyethylene, 0-30% by weight of regenerated ethylene vinyl copolymer, 0-10% by weight of ethylene-propylene copolymer, polyethylene graft. Resin composed of 10-20% by weight of maleic anhydride and 0-20% by weight of polypropylene graft maleic anhydride, 2-5 parts by weight of crosslinking agent, 10-15 parts by weight of blowing agent, and foaming aid 0-2 with respect to 100 parts by weight of the resin. It contains one or more additives of parts by weight, 0-2.5 parts by weight of internal mold release agent, 0-5 parts by weight of external mold release agent, 0-10 parts by weight of plasticizer, 0-2.5 parts by weight of heat transfer accelerator, and flame retardant 130- Flame retardant polyolefin crosslinked foam composition characterized by further containing 190 parts by weight of the composition.

The present invention is to optimize the processing conditions through the seal line extrusion experiment by the electron beam crosslinking method using a recycled resin, such as recycled polyethylene, regenerated ethylene vinyl acetate (EVA), the temperature of the cross-linking agent and the blowing agent in the extrusion process to 118 ℃ It maintains below, and not only adjusts the kneading speed in the range of 80-200 rpm, but also diversifies the electron beam irradiation method to induce the cell gradient of the foam, cell gradient excellent in environmental friendliness, economic efficiency, flame resistance, etc. It is an object to provide a low density polyolefin (particularly polyethylene) foam having

The present invention is a low density polyolefin foam having a cell gradient using an electron beam crosslinking technique, wherein 100 parts by weight of a resin in which a recycled low density polyethylene (LDPE) and a recycled ethylene vinyl acetate (EVA) copolymer are mixed in a weight ratio of 8: 2 to 6: 4. 2-5 parts by weight of crosslinking agent, 10-15 parts by weight of blowing agent, more than 0 parts by weight of 2 parts by weight or less of foaming aid, more than 0 parts by weight of 2.5 parts by weight of internal mold release agent, more than 0 parts by weight of 5 parts by weight of external mold release agent, plasticizer More than 0 parts by weight and 10 parts by weight or less, one or more additives of more than 0 parts by weight and 2.5 parts by weight or less, and 150-250 parts by weight of a flame retardant, and have a limiting oxygen index (LOI) of 28 or more and a carbonization rate (char yiled) is a flame-retardant low density polyolefin foam having about 45-55%, CO gas generation amount of about 0.11 kg / kg, smoke density (light transmittance in the smoke) of 97% or more, and UL-94 grade VO. By It provides a low density polyolefin foam.

The regenerated low density polyethylene preferably has a melting point of 100-130 ° C. and the regenerated ethylene vinyl acetate copolymer has a vinyl acetate content of 10-50% by weight. The weight ratio of regenerated low density polyethylene (LDPE) and regenerated ethylene vinyl acetate (EVA) copolymer is preferably 8: 2 to 6: 4, most preferably 7: 3.

The recycled low density polyethylene as waste resources is smaller than the molecular weight of pure polyethylene, and the molecular weight of the recycled ethylene vinyl acetate copolymer is also only 1/2 to 2/3 of the molecular weight of the pure ethylene vinyl acetate copolymer. Such regenerated low density polyethylene and regenerated ethylene vinyl acetate copolymers can be made much easier to crosslink compared to pure raw materials as well as to facilitate the foaming process.

In the present invention, the crosslinking agent is preferably an isopropylenebenzene or dicumylperoxide (DCP) as the peroxide crosslinking agent, and the blowing agent is organic such as azodicarbonamides (ACDC) or dinitrosopentamethylenetetramine (DPT). It is preferably a chemical blowing agent or an inorganic chemical blowing agent such as sodium bicarbonate (trade name: kycerol-91), more preferably azodicarbonamides (ACDC). In addition, as the foaming aid used for controlling the foamability and temperature affecting processability and productivity, urea foaming aid (trade name: Cellex-A) is preferable. As the internal mold release agent, polyethylene wax (LC-102N) and processing agent (MMA based acrylic processing aid) are preferable as rubber processing enhancers, and stearic acid is preferable when considering extrudability as the external mold release agent. The plasticizer is preferably diethylhexyl phthalate, paraffin oil or diphenylcresyl phosphates in consideration of compatibility with the resin, processability and foamability, and zinc oxide (ZnO) is preferable as the heat transfer accelerator.

In consideration of the environment and safety, flame retardants can be imparted and maximized by using inorganic flame retardants such as Al (OH) ₃ or Mg (OH) ₂ , phosphorus flame retardants, and nitrogen flame retardants. The flame retardant in the present invention is a polymer nanocomposite. (polymer nanocomposite, PNC), Al (OH) ₃ or Mg (OH) ₂ It is preferable to include at least one. In the present invention, the content of the flame retardant is preferably 150 to 250 parts by weight, and most preferably 200 parts by weight based on 100 parts by weight of the resin.

The low density polyolefin foam is preferably nano sized.

The low density polyolefin foam having a cell gradient using the electron beam crosslinking technique of the present invention is preferably subjected to cross-sectional irradiation of an electron beam of energy of 1, 2.5 MeV at an irradiation dose of preferably 40-60 kGy, more preferably 42-50 kGy. It may be optically crosslinked, or may be photocrosslinked by irradiating an electron beam of 1, 2.5 MeV energy on both sides of an electron beam of 15-30 kGy.

In addition, the present invention provides a method for producing a low density polyolefin foam having a cell gradient using an electron beam crosslinking technique, comprising: (a) 100 weight of a resin in which a recycled low density polyethylene and a recycled ethylene vinyl acetate copolymer are mixed in a weight ratio of 8: 2 to 6: 4. Parts, 2-5 parts by weight of crosslinking agent, 10-15 parts by weight of blowing agent, more than 0 parts by weight of 2 parts by weight or less of foaming aid, more than 0 parts by weight of 2.5 parts by weight of internal mold release agent, more than 0 parts by weight of 5 parts by weight of external mold release agent, Kneading 150 to 250 parts by weight of one or more additives of more than 0 parts by weight of a plasticizer and 10 parts by weight or less, and more than 0 parts by weight and 2.5 parts by weight or less of a heat transfer accelerator; (b) compounding at 130-140 ° C. at 100-200 rpm and then compounding at 110-120 ° C. at 100-150 rpm; (c) compressing by hot-press at 115-125 ° C. and then extruding with an extruder; And (d) irradiating the electron beam, followed by foaming at 160-190 ° C.

In the step (a), the kneading speed is preferably 80-200 rpm.

In the step (c), the internal temperature of the extruder is preferably 115-135 ℃.

In the step (d), one side light irradiation of the electron beam of 42-50 kGy or double side light irradiation of the electron beam of 15-30 kGy.

According to the present invention, by diversifying the electron beam irradiation method to induce a cell gradient of the foam, to prevent the spread of the flame in the outer portion of the foam having a small cell size, the limit oxygen index (LOI) is 28 or more, the carbonization rate ( char yiled), flame-retardant polyolefin (nano) foams with a 45-55% CO emissions, 0.11 kg / kg CO2, smoke density (light transmittance in the smoke) of 97% or more, and UL-94 grade VO. It can be manufactured environmentally, stably and economically.

The low density polyolefin foam having a cell gradient using the E-beam crosslinking technique according to the present invention has a limit of oxygen index (LOI) of 28 or more, a char yiled of about 45 to 55%, Flame retardant polyolefin foam with CO gas generation amount of about 0.11 kg / kg, smoke density (light transmittance in smoke) of more than 97%, and UL-94 grade of VO, and has excellent environmental friendliness, safety and economy. There is this.

The present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples, and those skilled in the art can understand that various modifications, modifications or applications are possible without departing from the technical spirit derived by the matters described in the appended claims. There will be.

Example

Regenerated low density polyethylene and a regenerated ethylene vinyl acetate copolymer were kneaded with a resin mixed in a weight ratio of 7: 3, at least one additive with a crosslinking agent, a foaming agent, a foaming aid, an internal release agent, an external release agent, a plasticizer, a heat transfer accelerator, and a flame retardant. . It was then compounded at about 130-140 ° C. at 100-200 rpm and then compounded at about 110-120 ° C. at 100-150 rpm. It was then compressed by hot-press at 115-125 ° C. and then extruded with an extruder (internal temperature: 115-135 ° C.). The polyolefin foams were prepared by photocrosslinking the specimens prepared in this manner by electron beam irradiation with different conditions. The electron beam cross-linking irradiation apparatus used an NHV electron beam processing system, and the irradiation dose was irradiated to the specimens produced in the seal line process by irradiating 42-50 kGy (3MeV) only in cross section, and the foaming characteristics and flame retardancy of these foams And the like. The flame-retardant polyolefin nanofoams crosslinked 15-30 kGy (1, 2.5 MeV) by double-sided irradiation using an electron beam irradiator manufactured by IBTECH Co., Ltd. were fabricated by irradiation apparatuses having different electron beam energies, that is, electron beam penetration depths. The cell gradient of the foam was observed. The irradiation dose was changed as well as the electron beam energy, and the effect of the electron beam energy and the dose on the cell gradient was observed. In order to produce a good foam having a flame retardancy of at least 28, the flame retardancy index (LOI) of 28 or more was prepared and used as a specimen containing a resin (100 parts by weight) and a flame retardant (200 parts by weight). The foaming properties, morphology, flame retardancy, smoke density, harmful gas concentration and the like of the foams were investigated.

The composition and electron beam dosage of the polyolefin foam specimens are as shown in Table 1 below.

Psalter
                        Composition (parts by weight): gross weight (70 g) Suzy
                Flame retardant Electron beam blowing agent Conventional flame retardant Mg (OH) ₂ Al (OH) ₃ PNC 3MeV (kGy) ADCA One 100 120 0 0 0 42.5-50.0 18 2 100 120 0 0 2.5 42.5-50.0 18 3 100 120 20 0 0 42.5-50.0 18 4 100 120 20 0 2.5 42.5-50.0 18 5 100 120 40 0 0 42.5-50.0 18 6 100 120 40 0 2.5 42.5-50.0 18 7 100 120 40 40 0 42.5-50.0 18 8 100 120 40 40 2.5 42.5-50.0 18

Table 2 below shows the light irradiation of the specimens.

Irradiation dose
(D, kGy) Number of times Beam current
(I, mA) speed
(V, m / min) Acceleration voltage 42.5 One 20.9 3 3MeV 45.0 One 22.1 3 3MeV 47.5 One 23.3 3 3MeV 50.0 One 24.5 3 3MeV

I (mA) = (k * D * V) + I (mA) Loss, k = 0.1624, I (mA) Loss = 0.16

Table 3 below shows the light irradiation (single-sided irradiation and double-sided irradiation) of the specimens.

Psalter Acceleration voltage Over dosage
(kGy) Rear dose
(kGy) Acceleration voltage Over dosage
(kGy) 9 2.5MeV 30 0 1MeV 15 10 2.5MeV 30 0 1MeV 20 11 2.5MeV 30 0 1MeV 25 12 2.5MeV 30 0 1MeV 30 13 2.5MeV 30 30 1MeV 15 14 2.5MeV 30 30 1MeV 20 15 2.5MeV 30 30 1MeV 25 16 2.5MeV 30 30 1MeV 30

As shown in Figures 2a to 2d, Specimen 2, unlike specimens 4 and 6, does not contain an inorganic flame retardant, Mg (OH) ₂ , which is a foam containing less flame retardant, but having poor surface properties. It was observed that the foam using Mg (OH) ₂ as a flame retardant showed better surface properties than the foam containing Al (OH) ₃ only. On the other hand, the surface properties of the flame retardant polyolefin foam produced by photocrosslinking were superior to the flame retardant polyolefin foam prepared by chemical crosslinking. The foam has a closed cell structure and the cell size is relatively constant from 0.4 to 0.23, with a slight cell gradient but not clear. In addition, the foaming rate and the cell size tended to decrease as the electron beam irradiation amount increased, which may be explained by the increase in the crosslinking rate as the irradiation amount increased. The increase in the amount of flame as well as the amount of flame retardant decreased the foaming rate and the cell size, which is almost identical to the flame retardant polyolefin foam produced by the chemical crosslinking method.

Tables 4 to 7 below show foaming characteristics of the polyolefin foam according to the flame retardant (in Table 4, the irradiation dose is 42.5 kGy, in Table 5, the irradiation dose is 45.0 kGy, and in Table 6, the irradiation dose is 47.5 kGy. Table 7 shows an irradiation dose of 50.0 kGy).

Psalter Firing time /
Request time
(° C / min) Inflatable
(%) surface Cell structure Cell size
(mm) LOI Degree of crosslinking One 160-190 / 30 2035 Good Closed cell
Uniformity 0.40 24.2 27.5 2 160-190 / 30 1975 Good Closed cell
Uniformity 0.40 24.4 27.6 3 160-190 / 30 1879 Good Closed cell
Uniformity 0.37 25.4 27.3 4 160-190 / 30 1824 Good Closed cell
Uniformity 0.36 25.5 27.1 5 160-190 / 30 1691 Good Closed cell
Uniformity 0.30 26.2 26.9 6 160-190 / 30 1634 Good Closed cell
Uniformity 0.31 26.5 27.2 7 160-190 / 30 1318 Good Closed cell
Uniformity 0.25 27.8 25.4 8 160-190 / 30 1300 Good Closed cell
Uniformity 0.23 28.2 25.0

Psalter Firing time /
Request time
(° C / min) Inflatable
(%) surface Cell structure Cell size
(mm) LOI Degree of crosslinking One 160-190 / 30 2000 Good Closed cell
Uniformity 0.23-0.36 24.2 27.7 2 160-190 / 30 1910 Good Closed cell
Uniformity 0.23-0.36 24.4 27.6 3 160-190 / 30 1750 Good Closed cell
Uniformity 0.23-0.36 25.4 28.3 4 160-190 / 30 1716 Good Closed cell
Uniformity 0.23-0.35 25.5 28.1 5 160-190 / 30 1660 Good Closed cell
Uniformity 0.23-0.35 26.2 27.9 6 160-190 / 30 1600 Good Closed cell
Uniformity 0.23-0.32 26.5 28.2 7 160-190 / 30 1238 Good Closed cell
Uniformity 0.23-0.30 27.8 28.0 8 160-190 / 30 1230 Good Closed cell
Uniformity 0.23-0.30 28.2 29.0

Psalter Firing time /
Request time
(° C / min) Inflatable
(%) surface Cell structure Cell size
(mm) LOI Degree of crosslinking One 160-190 / 30 1935 Good Closed cell
Uniformity 0.23-0.36 24.2 27.3 2 160-190 / 30 1898 Good Closed cell
Uniformity 0.23-0.36 24.4 27.2 3 160-190 / 30 1684 Good Closed cell
Uniformity 0.23-0.36 25.4 28.3 4 160-190 / 30 1682 Good Closed cell
Uniformity 0.23-0.35 25.5 27.3 5 160-190 / 30 1559 Good Closed cell
Uniformity 0.23-0.35 26.2 27.9 6 160-190 / 30 1520 Good Closed cell
Uniformity 0.23-0.32 26.5 28.2 7 160-190 / 30 1230 Good Closed cell
Uniformity 0.23-0.29 27.8 29.5 8 160-190 / 30 1236 Good Closed cell
Uniformity 0.23-0.29 28.2 29.1

Psalter Firing time /
Request time
(° C / min) Inflatable
(%) surface Cell structure Cell size
(mm) LOI Degree of crosslinking One 160-190 / 30 1900 Good Closed cell
Uniformity 0.23-0.36 24.2 28.4 2 160-190 / 30 1898 Good Closed cell
Uniformity 0.23-0.36 24.4 28.0 3 160-190 / 30 1650 Good Closed cell
Uniformity 0.23-0.36 25.4 29.3 4 160-190 / 30 1650 Good Closed cell
Uniformity 0.23-0.35 25.5 29.3 5 160-190 / 30 1520 Good Closed cell
Uniformity 0.23-0.35 26.2 30.9 6 160-190 / 30 1525 Good Closed cell
Uniformity 0.23-0.32 26.5 30.2 7 160-190 / 30 1210 Good Closed cell
Uniformity 0.23-0.26 27.8 31.5 8 160-190 / 30 1205 Good Closed cell
Uniformity 0.23-0.26 28.2 31.1

As shown in Figure 3, comparing the carbonization rate of the polyolefin foam and LOI, the amount of flame retardant, in particular the amount of PNC produced a foam that meets the goal of producing a polyolefin nano-foam excellent flame retardancy.

As shown in FIG. 7, the irradiation dose was constant at 45 kGy, and as the amount of the flame retardant increased, the temperature at 0.5% of the initial decomposition tended to increase, which was initially due to a decrease in the ratio of resin to flame retardant. This is because the amount of resin affecting the decomposition is relatively small, and as the amount of the flame retardant increases, the residue increases. This is a theoretical data and the same trend was observed in thermogravimetric analysis containing 2.5 parts by weight of PNC. However, it was observed that the polyolefin foam containing the amount of the flame retardant to 200 parts by weight relative to 100 parts by weight of the resin did not differ significantly from the thermal stability of the crosslinking degree or the electron beam irradiation amount.

Table 8 below shows TGA data of electron beam irradiated polyolefin foams containing flame retardant.

Psalter
T _d (℃) Residual amount
(Wt%; 887 ° C.) 99.5% 90.0% 70.0% Max One 130.4 254.8 375.1 384.1 39.0% 2 120.9 254.0 375.1 384.2 38.5% 3 120.8 259.9 378.9 386.4 40.4% 4 117.5 276.3 380.8 386.8 40.1% 5 137.5 269.0 377.6 387.5 44.7% 6 137.5 278.0 379.3 388.3 44.2% 7 134.3 296.3 386.0 390.8 47.1% 8 138.0 282.8 381.5 389.8 46.5%

Table 9 below shows the THA data of the flame retardant polyolefin foam according to the electron beam irradiation amount.

T _d (℃) Residual amount
(Wt%; 887 ° C.)
99.5% 90.0% 70.0% Max Chemical-X 138.0 266.3 379.8 388.8 46.1%

Photo-x
42.5 kGy 138.4 271.3 379.5 386.6 46.3% 45.0 kGy 138.0 282.8 381.5 389.8 46.5% 47.5 kGy 138.3 272.3 379.9 388.5 46.3% 50.0 kGy 138.2 270.3 378.1 386.5 46.4%

In the manufacture of the polyolefin foam as shown in Table 3, the specimens 9 to 12 were irradiated with electron beam energy of 2.5 MeV at 30 kGy on the front surface, and 15, 20, 25, and 30 kGy of electron beam energy on the rear surface were irradiated with 15 kVy. The specimens 13 to 16 were prepared by irradiating electron beam energy of 2.5 MeV at 30 kGy on the front and rear surfaces, and 15, 20, 25, and 30 kGy at 1 MeV on the rear surface.

Specimens 9-12 exhibited a relatively low foaming rate of 1050-1120%, but a foaming rate of 100% or more. It was observed that the cell size of 0.26-0.27 was uniformly distributed in the range of 10-13 mm of the irradiation surface. Braille beam penetration depth of 2 MeV has been reported in the literature as 13 mm, but effective electron beam penetration depth is estimated to be 7-8 mm. The LOI (Limit Oxygen Index) of these foams showed a relatively high flame retardant characteristic of 29.5-29.7, which can be explained by the role of preventing the spread of flame in the region having 3mm / 0.1mm cells. As a result of measuring the degree of crosslinking of specimens 9-12, it was in the range of 23.5-24.5, which is expected to have an electron beam penetration depth of about 1-2 mm of 1 MeV, and more than 3 mm of uncrosslinked parts could not form cells when foamed and melted. It seems to have been. This can also be observed in the cell structure, where cells do not exist at a cell depth of about 3 mm, which is consistent with the bulky appearance. Specimen 13 to 16 had a relatively high foaming rate of 1400-1540%, and cell gradients were observed in irradiated specimens of 1 MeV 20 kGy or more (Samples 14 to 16). As a result, it was predicted that not only the cell gradient but also the overall LOI value gave a high flame retardancy of 29.7-30.0. The foam has a structure in which the cell size is approximately 3 mm from the foam surface of the portion smaller than 0.2 mm and the 2.6 mm cells are uniformly distributed.

Table 10 below shows the foaming properties of the polyolefin foam according to the flame retardant.

Psalter Firing time /
Request time
(° C / min) Inflatable
(%) surface Cell structure Cell size
(mm) LOI Degree of crosslinking 9 160-190 / 30 1050 Good Closed cell
Uniformity 0.1-0.26 29.5 23.5 10 160-190 / 30 1090 Good Closed cell
Uniformity 0.1-0.26 29.6 24.1 11 160-190 / 30 1100 Good Closed cell
Uniformity 0.1-0.27 29.7 23.9 12 160-190 / 30 1120 Good Closed cell
Uniformity 0.1-0.27 29.7 24.5 13 160-190 / 30 1400 Good Closed cell
Uniformity 0.2-0.30 29.7 30.5 14 160-190 / 30 1450 Good Closed cell
Uniformity 0.2-0.31 29.8 30.9 15 160-190 / 30 1518 Good Closed cell
Uniformity 0.3-0.31 29.8 30.8 16 160-190 / 30 1540 Good Closed cell
Uniformity 0.3-0.32 30.0 30.9

Table 11 below shows the flame retardant properties of polyolefin foams that were electron beam irradiated with different dosages.

Psalter Inflatable
(%) Cell size
(mm) Light transmittance
(%) UL-94
Afterglow time (sec) LOI UL-94 Average CO Gas Generation
(kg / kg) Carbonization rate
(%) 9 1050 0.1-0.26 98.0 0 29.5 V-O 0.110 50.9 10 1090 0.1-0.26 98.1 0 29.6 V-O 0.109 51.0 11 1100 0.1-0.27 97.8 0 29.7 V-O 0.109 50.0 12 1120 0.1-0.27 97.9 0 29.7 V-O 0.109 50.3 13 1400 0.2-0.30 97.1 0 29.7 V-O 0.109 48.0 14 1450 0.2-0.31 98.3 0 29.8 V-O 0.109 49.6 15 1518 0.2-0.31 98.1 0 29.8 V-O 0.113 49.4 16 1540 0.2-0.32 98.8 0 30.0 V-O 0.111 49.1

The electron beam crosslinking method has an effect on the cell structure, size, and cell gradient, but has excellent flame retardancy with LOI value of 29.5-30.0 and zero flame time, and does not significantly affect the flame retardancy. From the light transmittance of the smoke from the LOI measuring device, it was found that the smoke density was low with a light transmittance of about 97.1-98.8% from the data on securing the field of view in case of fire. In addition, the char yield measured the carbonization rate of the sample exposed to the 30 second flame from UL-94, and the carbonization rate was at most 50% or more. Moreover, CO gas generation amount was 0.11-0.113 and obtained the comparatively low value.

1 is a manufacturing process diagram of a low density polyolefin foam having a cell gradient using an E-beam crosslinking technique according to the present invention.

2A to 2D are photographs showing the surface of electron beam crosslinked polyolefin nanofoams containing different flame retardants (FIG. 2A: Specimen 2, FIG. 2B: Specimen 4, FIG. 2C and 2D: Specimen 6).

3 is a graph showing the limit oxygen index (LOI) and the carbonization rate of polyolefin foam.

4A-4H are images of cell structures of electron beam irradiated polyolefin foams (45.0 kGy) containing different flame retardants (FIG. 5A: Specimen 1, 5B: Specimen 2, FIG. 5C: Specimen 3, FIG. 5D: Specimen 4 5E: Psalm 5, FIG. 5F: Psalm 6, FIG. 5G: Psalm 7, FIG. 5H: Psalm 8).

5A-1, 5B-1, 5C-1 and 5D-1 are scanning electron micrographs of the cell structure of polyolefin nanofoams containing different flame retardants, and FIGS. 5A-2, 5B-2, 5C-2 and 5D -2 is a scanning electron micrograph of the dispersion of polyolefin nanofoams containing different flame retardants (FIGS. 5A-1 and 5A-2: Specimen 2, 5B-1 and 5B-2: Specimen 4, 5C-1) And 6c-2: specimen 6, FIGS. 5D-1 and 5d-2: specimen 6).

6A-6D are images of cell structures of polyolefin foams (Sample 9) that were electron beam irradiated at different relative doses (FIG. 6A: 42.5 kGy, FIG. 6B: 45.0 kGy, FIG. 6C: 47.5 kGy, FIG. 6D: 50.0 kGy).

FIG. 7 shows the TGA curves of electron beam irradiated polyolefin foams containing flame retardants.

8 shows the TGA curve of the flame retardant polyolefin foam according to the electron beam irradiation amount.

9A to 9H are photographs of polyolefin foams irradiated with electron beams by different irradiation methods (FIG. 9A: Specimen 9, 9B: Specimen 10, FIG. 9C: Specimen 11, FIG. 9D: Specimen 12, FIG. 9E: Specimen 13, and FIG. 9F). : Psalm 14, FIG. 9G: Psalm 15, FIG. 9H: Psalm 16).

10A and 10B are photographs of polyolefin foams that were electron beam irradiated with different irradiation methods (FIG. 10A: Specimen 9-12, FIG. 10B: Specimen 13-16).

11A-11H are images of cell structures of electron beam irradiated polyolefin foams at different irradiation speeds (FIG. 11A: Specimen 9, FIG. 11B: Specimen 10, FIG. 11C: Specimen 11, FIG. 11D: Specimen 12, FIG. 11E: Psalm 13, FIG. 11F: Psalm 14, FIG. 11G: Psalm 15, FIG. 11H: Psalm 16).

Claims (5)

A low density polyolefin foam having a cell gradient using electron beam crosslinking technology, 100 parts by weight of the mixed resin having a low density polyethylene and a regenerated ethylene vinyl acetate copolymer in a weight ratio of 8: 2 to 6: 4, 2-5 parts by weight of crosslinking agent, 10-15 parts by weight of blowing agent, and more than 0 parts by weight of foaming aid. At least 0 parts by weight, at least 0 parts by weight of the internal mold release agent, at least 5 parts by weight, at least 0 parts by weight of the external release agent, at least 10 parts by weight, at most 0 parts by weight of the plasticizer, , Contains 150-250 parts by weight of flame retardant, A limiting oxygen index (LOI) of 28 or more, char yiled of about 45 to 55%, CO gas generation of about 0.11 kg / kg, smoke density (light transmittance in the smoke) of 97%, A low density polyolefin foam characterized by being a flame retardant low density polyolefin foam having a UL-94 grade of VO. The method of claim 1, The low density polyolefin foam is low density polyolefin foam, characterized in that the nano (nano) size. The method of claim 1, The flame retardant comprises at least one of polymer nanocomposite (PNC), Al (OH) ₃ or Mg (OH) ₂ , the blowing agent is a low density polyolefin foam, characterized in that azodicarbonamides (ADCA) . The method according to any one of claims 1 to 3, A low-density polyolefin foam characterized by photocrosslinking by a method of cross-sectional irradiation of an electron beam of energy of 1, 2.5 MeV at an irradiation dose of 40-60 kGy. The method according to any one of claims 1 to 3, A low density polyolefin foam characterized by photocrosslinking by a method of irradiating an electron beam of energy of 1, 2.5 MeV at both sides with a dose of 15-30 kGy.

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