JP5793912B2 - Flame retardant comprising highly hydrated mafic slaked lime as an active ingredient, method for producing the same, and thermoplastic polymer containing the same - Google Patents

Description

The present invention relates to a flame retardant containing a highly hydrated mafic slaked lime as an active ingredient, and also includes a production method thereof. The present invention further relates to a thermoplastic polymer composition blended with the flame retardant to make it flame retardant. Here, the thermoplastic polymer includes both a thermoplastic resin and an elastomer. The flame retardant of the present invention has the greatest advantage that no toxic halogen gas is generated during the combustion of the flame retardant thermoplastic polymer using the flame retardant. When this flame retardant is blended with a flammable polyolefin material among thermoplastic polymers, the significance thereof is best exhibited.

Thermoplastic polymers are directed to various uses such as films, sheets, pipes, containers, covered wires, cables, materials for electronic parts, and the like by various methods such as extrusion molding and injection molding. Among such thermoplastic polymers, those of polyolefin type in particular are relatively flammable materials, and the oxygen index, which is one of flammability indicators, is about the oxygen concentration in the air itself. It shows a value lower than 21% and burns even in an atmosphere having a lower oxygen concentration than air. Therefore, it is often necessary to make it flame-retardant from the viewpoint of disaster prevention.

In order to make various polymer materials flame retardant, it is widely practiced to add a flame retardant to the material. There are many types of flame retardants, but they can be broadly divided into halogen compounds (bromine compounds and chlorine compounds), phosphorus compounds, nitrogen-containing compounds, hydrated metal compounds and other inorganic compounds. is there. Halogen compound flame retardants have the ability to increase flame retardancy with a small amount, but also have the disadvantage of generating toxic halogen gas during combustion. is there. In particular, the use of some brominated compounds is prohibited in Europe based on the WEEE directive and the RoHS directive. Due to this influence, the use of flame retardants mainly composed of halogen compounds tends to be gradually avoided throughout the world including Japan.

Some phosphorous compound flame retardants act as environmental hormones, and some generate toxic gases of phosphines, which are also concerned about their use. Hydrated metal compound flame retardants are non-halogen based and are currently used as the main flame retardants for eco-cables. The flame retardant performance of hydrated metal compounds is based on dehydration and endothermic reactions and the heat insulation and oxygen barrier effects of oxide layers. As a typical hydrated metal compound, magnesium hydroxide dehydrates and absorbs heat in a temperature range of 350 to 450 ° C. On the other hand, aluminum hydroxide is thermally decomposed and dehydrated at 250 to 350 ° C. to absorb heat.

For this reason, when making a thermoplastic polymer flame-retardant by blending a hydrated metal compound, an appropriate flame retardant must be selected in consideration of the molding temperature and thermal decomposition temperature of the thermoplastic polymer. . From this point of view, magnesium hydroxide is suitable for use as a material that thermally decomposes and burns around 400 ° C., and aluminum hydroxide is suitable for a material that pyrolyzes and burns around 300 ° C. The specific thermal decomposition and combustion temperatures of thermoplastic resins are about 480 ° C. for polyethylene, about 400 ° C. for polypropylene, and about 370 ° C. to about 450 ° C. for ethylene / vinyl acetate copolymer. Usually, magnesium hydroxide or a combination of magnesium hydroxide and aluminum hydroxide is selected. Polyvinyl chloride thermally decomposes and burns at about 300 ° C., so aluminum hydroxide is used for this.

There is brucite, a natural mineral, as a resource for magnesium hydroxide, but its production is mainly overseas, and it may contain asbestos, which may cause harm to the human body. is not. Aluminum hydroxide is manufactured from bauxite, but there is a tendency for domestic aluminum refining to be abolished, and there is a problem with the disposal of red mud produced as a by-product. It has become difficult.

When flame retardancy is imparted by blending a hydrated metal compound with a thermoplastic polymer, a large amount of blending is required to obtain high flame retardancy. However, if a large amount is added, the physical properties and molding processability of the thermoplastic polymer are lowered, so that the amount is naturally limited. In order to alleviate this problem, in recent years, countermeasures have been taken such as the formation of fine particles of hydrated metal compounds, the control of the particle shape, and the surface treatment. In addition, flame retardants in which other substances are added to hydrated metal compounds as flame retardant aids have been developed. For example, there is a proposal of a magnesium hydroxide flame retardant having a controlled particle size and particle shape (Patent Document 1), which includes magnesium hydroxide surface-treated with a nickel compound and aluminum hydroxide surface-treated with nitrate. .

In a recent development example, there is a composite flame retardant (Patent Document 2) of magnesium hydroxide and a hydrolyzate of a titanium compound. However, in this flame retardant, in addition to the problem that the titanium compound is a relatively expensive material, the titanium oxide produced in the hydrolyzate has a photocatalytic ability, and the deterioration of the thermoplastic synthetic resin containing the flame retardant is prevented. There is also the problem of causing it.

As an example of blending a flame retardant composed of a hydrated metal compound into a polyolefin-based material, a flame retardant was improved by using a halogen-based flame retardant and antimony trioxide in combination with polyolefin in addition to aluminum hydroxide or magnesium hydroxide. Although a composition has been proposed (Patent Document 3), this technique does not provide a new flame retardant, but blends a known flame retardant. In addition, there is a composition in which flame retardancy is imparted by blending magnesium hydroxide or aluminum hydroxide with a thermoplastic polymer made of an ethylene (co) polymer (Patent Document 4). There, calcium and magnesium hydrates are listed as inorganic flame retardants, but their specific properties are not specified.
JP2007-016152A JP2010-030882 Japanese Patent No. 2919299 Registration No. 3364389

The inventors have conceived of using as a flame retardant lime slaked lime obtained by calcining and digesting dolomite, and investigated the thermal decomposition behavior of lime slaked lime, which is useful as a flame retardant. It was confirmed that. Further, the inventors have pursued an appropriate hydration rate of MgO in the calcined dolomite, an appropriate particle size, etc., and have identified a mafic slaked lime suitable as a flame retardant and established a production method thereof.

A general object of the present invention is to provide a flame retardant of a thermoplastic polymer containing, as an active ingredient, a calcined lime obtained by calcining and digesting dolomite, and therefore no generation of toxic halogen gas, and a method for producing the same. It is to provide. A specific object of the present invention is to apply the flame retardant of the present invention to a flammable polyolefin-based material among thermoplastic polymers and to impair the moldability despite having high flame retardancy. It is an object to provide a thermoplastic polymer composition that is not damaged. A more specific object of the present invention is to provide a flame retardant thermoplastic polymer imparting flame retardancy to an ethylene / vinyl acetate copolymer, which is particularly suitable for the flame retardant of the present invention, among polyolefin polymer materials. It is to provide.

A flame retardant that achieves the general object of the present invention is a clay slaked lime obtained by calcining and digesting dolomite, and the hydration rate of magnesium oxide therein is 85.7 % or more. It is a flame retardant for thermoplastic polymers containing hydratable mashed slaked lime as an active ingredient.

The method for producing a flame retardant, which is also the object of the general purpose of the present invention, is to calcite dolomite and add water to digest it into a clay slaked lime .
(A) The water ratio of digested water is in the range of 0.4 to 0.9,
(B) After completion of digestion, the adhesion moisture of the mashed slaked lime when shifting to aging is in the range of 5 to 20% by weight.
Is carried out under conditions satisfying at least one of these, preferably both , and aging is carried out under conditions of an atmospheric temperature of 80 to 120 ° C. and a time of 12 to 48 hours. It is characterized by being 85.7% or more .

The flame-retardant thermoplastic polymer composition that achieves the specific object of the present invention is a highly hydrated magnesium oxide having a hydration rate of 60% or more with respect to 100 parts by weight of the thermoplastic resin or thermoplastic elastomer. It is a flame retardant thermoplastic polymer composition comprising 50 to 250 parts by weight of a flame retardant containing hydratable clay slaked lime as an active ingredient. The flame retardant thermoplastic polymer composition for a more specific purpose of the present invention is an ethylene / vinyl acetate copolymer having a vinyl acetate component content of 15% or more with respect to 100 parts by weight. A flame-retardant thermoplastic resin composition comprising 50 to 250 parts by weight of the flame retardant of the present invention, and preferably 50 to 100 parts by weight for molding.

In general, a thermoplastic resin is thermally decomposed in a temperature range of 350 to 500 ° C., and a combustible gas is generated to expand a combustion range. As data showing the thermal decomposition characteristics, differential thermal analysis curves of typical polyolefins such as polypropylene, ethylene / vinyl acetate copolymer, low density polyethylene and ethylene / ethyl acrylate copolymer are shown in FIG. On the other hand, as data showing the thermal decomposition / dehydration characteristics of the hydrated metal compound, the differential thermal analysis curves of the mashed slaked lime, calcium hydroxide, magnesium hydroxide and aluminum hydroxide are shown in FIG. Comparing FIG. 1 and FIG. 2, it is clear that the highly hydrated clay slaked lime causes dehydration and endothermic reaction in the temperature range where the above thermoplastic resin is thermally decomposed to generate combustible gas. is there. Since the behavior of both of them is similar to each other, the composition containing highly hydrated mashed slaked lime in the thermoplastic resin is capable of dehydrating and endothermic reaction of the mashed slaked lime simultaneously with the thermal decomposition of the thermoplastic resin. It happens and produces a flame retardant effect. In addition, the pyrolysis product of mashed slaked lime exhibits heat insulation, oxygen barrier and gas barrier performance, suppresses the emission of combustible gas, contributes to flame retardancy by reducing combustion.

As shown in the data of Examples to be described later, the flame retardant thermoplastic polymer composition of the present invention does not lose the moldability inherent to the thermoplastic polymer even at a high flame retardant blending ratio. Can be easily processed into molded products. Since the flame retardant of the present invention does not contain a halogen element, there is no problem of generation of halogen gas even during combustion. Mafic slaked lime can be produced domestically, is supplied stably, is an inexpensive material, and does not contain asbestos, which is harmful to the human body. Thus, the flame retardant and flame retardant thermoplastic polymer composition of the present invention are safe and effective environmentally friendly.

As described above, the flame retardant of the present invention is obtained by calcining dolomite (nCaCO ₃ .mMgCO ₃ ) and digesting (hydrating) calcined dolomite (nCaO · mMgO) as water. An effective ingredient is slaked lime. Baking is performed using a rotary kiln or shaft kiln, and digestion is performed using a digester. Of these steps, calcination may be carried out in accordance with known techniques for calcining dolomite, but digestion needs to achieve a higher hydration rate than conventional mafic slaked lime. To meet the requirements.
The mashed slaked lime has the formula nCa (OH) ₂ · (1-m) MgO · mMg (OH) ₂ (n · m represents the amount of substance)
Where n is given by the composition of the raw dolomite and m is determined by the digestion conditions. In general, the mould slaked lime used as a building material or fertilizer is sufficient for incomplete digestion, so the value of m in the above formula is often less than 0.3, for example, but it is used as a flame retardant In this case, since the dehydration and endothermic performance is required for the hydrated metal compound, it is necessary to make the hydration more complete and the value of m is close to 1.

Table 1 shows the results of analysis of a certain bitter slaked lime by JIS R 9011 “Testing method of lime”.
Table 1 Chemical analysis value of weightless slaked lime A (% by weight)

Calculation of the hydration rate of MgO in the clay slaked lime A based on the numerical values in Table 1 is as follows.
1) Ig.Loss indicates the sum of the amount of hydroxyl group, carbon dioxide (decarboxylated) and moisture (attached water) contained in the mashed slaked lime. Therefore, the amount of hydroxyl groups is represented by the following formula.
Amount of hydroxyl group (% by weight) = Ig. Loss− (CO ₂ + water) = 25.4− (5.9 + 0.3) = 19.2
2) CO ₂ is considered to be derived from calcium carbonate contained in the clay slaked lime. Therefore, the amount of digested CaO in the mashed slaked lime is expressed as the difference between the total CaO amount and the CaO amount derived from calcium carbonate.
Digested CaO (% by weight) = total CaO— (CO ₂ × 56.1 / 44.0) where 56.1 is the formula weight of CaO and 44.0 is the molecular weight of CO ₂ .
3) CaO and MgO each react with an equal amount of H ₂ O. That is,
CaO + H ₂ O → Ca (OH) ₂ , MgO + H ₂ O → Mg (OH) ₂
Further, since the hydration reactivity of CaO is higher than that of MgO, CaO is preferentially hydrated and then MgO is hydrated. Therefore, the amount of water required for CaO digestion is represented by the product of the digested CaO substance amount and the water molecular weight.
Amount of water required for digestion of CaO (% by weight) = (digested CaO / 56.1) × molecular weight of H ₂ O = (41.6 / 50.1) × 18 = 13.3
4) The amount of water required for MgO digestion is indicated by the difference between the amount of hydroxyl groups and the amount of water required for CaO digestion.
Amount of water (% by weight) required for digestion of MgO = 19.2-13.3 = 5.9
5) The digested amount of MgO is represented by the product of the amount of water required for digesting MgO and the formula amount of MgO.
Digested MgO amount (% by weight) = (5.9 / 18) × 40.3 = 13.2
6) The amount of undigested MgO is determined by the difference between the total amount of MgO and the amount of digested MgO.
Undigested MgO amount (% by weight) = 24.5-13.2 = 11.3
7) The hydration rate (%) of the mashed slaked lime is derived as a value obtained by dividing the digested MgO amount by the total MgO amount.
Hydration rate (%) = (13.2 / 24.5) × 100% = 53.9%
8) The content ratio of Mg (OH) ₂ in the mashed slaked lime is represented by the product of the amount of water required for digesting MgO and the formula amount of Mg (OH) ₂ .
Mg (OH) ₂ content ratio (% by weight) = (5.9 / 18) × 58.3 = 19.1
By the above calculation method, the hydration rate of MgO and the content ratio of Mg (OH) ₂ in the mashed slaked lime are obtained.

The amount ratio of calcium carbonate and magnesium carbonate composing dolomite varies slightly depending on the production area. What is used in the examples of the present invention to be described later has a mass ratio of about 6: 4. Therefore, the calcined dolomite obtained by calcining it has a formula of approximately 0.6 CaO · 0.4 MgO. It is represented by When hydrating this, ideally CaO (MgO) and H ₂ O are of equal mass,
0.6CaO · 0.4MgO + 1.0H ₂ O = 0.6Ca (OH) ₂ + 0.4Mg (OH) ₂
React with. Therefore, the amount of water (H ₂ O) required to hydrate 49.8 g of calcined dolomite (CaO · MgO) is 18 g. Here, the amount of water used to hydrate a certain amount of calcined dolomite is called “water ratio”, and the value of 18 / 49.8 = 0.36 in this case is called “equivalent water ratio”. Since the above hydration reaction is an exothermic reaction and the added water evaporates, more water than the equivalent water ratio is added in actual production. When using a dolomite other than the calcium carbonate / magnesium carbonate mass ratio of 6: 4, the “water ratio” and “equivalent water ratio” may be adjusted accordingly.

The specific digestion process starts by first pulverizing the calcined dolomite into an appropriate size, adding it to the digester and adding a predetermined amount of water. After digestion reaction for several tens of minutes, move to a ripening machine and leave or stir for a predetermined time. Ripening is a process necessary to complete the hydration of magnesium oxide, and is a process of “laying down” moistened lime slaked lime for a long time. Once ripening is complete, dry pulverized lime is dried, ground, and classified using an airflow-type drying / classifying machine such as an air separator or dry-meister, and a grinding machine such as a vibration mill or a ball mill to prepare a predetermined particle size. Collect things.

The amount of water to be added in the digester is selected from the range of 0.4 to 0.9 in terms of water ratio. At water ratios not reaching 0.4, digestion is inadequate as a result of the loss of water by evaporation. From the viewpoint of sufficient digestion of MgO, a high water ratio is advantageous, but when the water ratio exceeds 0.9, there is a lot of water adhering to the mashed slaked lime immediately after digestion, and thus aggregated As a result, the fluidity becomes poor, making it difficult to transfer to the next step, and drying requires time and energy. As conditions for the aging of the mashed slaked lime, it is desirable that the amount of water adhering to the aging after digestion is 5 to 20% by weight. If it is less than 5% by weight, water evaporates during aging, and hydration does not proceed to a high degree. When it exceeds 20% by weight, the same problem as when an inappropriately high water ratio is employed, that is, agglomeration, or the like occurs.

As can be easily understood, the water ratio and the amount of attached water after digestion are related, and an appropriate water ratio is advantageous in achieving an appropriate amount of attached water. Digestion and ripening satisfying at least one of the water ratio and the amount of adhering water, preferably both, give a highly hydratable clay slaked lime suitable as a flame retardant. The atmospheric temperature during aging is suitably 80 to 120 ° C. A suitable aging time is 12 to 48 hours. Digestion tends to be incomplete when ripening for a short time that does not reach 12 hours. On the other hand, digestion can be completed completely when aging for over 48 hours, but carbonation of calcium hydroxide may progress during that time. There is.

As described above, the hydration rate of magnesium oxide in the flame retardant of the present invention is required to be 85.7 % or more. The hydration rate is as high as possible and is preferably close to 100%. A high hydration rate means that the content of magnesium hydroxide is large, and the flame retardancy caused by the dehydration and endotherm is higher. Conventional bituminous slaked lime distributed as building and agricultural materials has a hydration rate of MgO of 60% or less, and even if used as a flame retardant, its effect is poor.

The flame retardant of the present invention preferably has a primary particle size in the range of 0.2 to 5 μm, and more preferably 0.8 to 2 μm. If it is fine, it is easy to mix with the thermoplastic polymer, and the flame-retardant thermoplastic composition has high moldability. However, those with extremely small particle diameters are difficult to industrially produce and are disadvantageous in terms of cost.

Even if the flame retardant of the present invention is directly added to a thermoplastic polymer, it naturally provides flame retardancy. However, the surface treatment with a specific organic compound increases the flame retardant effect. The surface treatment with an organic compound changes the surface of the flame retardant which is hydrophilic to hydrophobic, and improves the affinity with the thermoplastic polymer. Thereby, the dispersibility of the flame retardant in the thermoplastic polymer is improved. Specific organic surface treatment agents include organic acid anhydride / α-olefin copolymers, alcohols, silane coupling agents, titanate coupling agents, and fatty acids. Among them, an organic acid anhydride / α-olefin copolymer is particularly suitable. Diffusion mixers (Henschel mixer, super mixer), ball mill and bead mill are preferred for organic surface treatment of flame retardants. When using a solid surface treating agent, it is desirable to heat and melt in advance.

The flame retardant of the present invention can be blended with an arbitrary thermoplastic polymer to give flame retardancy. Particularly, the thermoplastic polymer for which the flame retardant is useful is a flammable polyolefin material. Specific examples include polyethylene, polypropylene, ethylene / methyl acrylate copolymer, ethylene / ethyl acrylate copolymer, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, and ethylene / vinyl acetate copolymer. . In particular, when applied to an ethylene / vinyl acetate copolymer, an excellent flame retardant effect is obtained.

As a method for producing a flame retardant composition by blending the flame retardant of the present invention with a thermoplastic polymer, there is a melt kneading using a mixing roll, an extruder-type kneader, a roll kneader, a high-speed biaxial continuous mixer, or the like. . Thereby, a pellet can be manufactured and processed by known techniques such as injection molding and extrusion molding to obtain a product.

Production of highly hydrated mashed slaked lime The calcined dolomite was digested under the conditions shown in Table 2 below to produce 4 types of mashed slaked lime. The aging time is 24 hours for all. In Table 2, sample A is a comparative example, and B to D are examples. An electron micrograph of Sample D is shown in FIG.

Table 2 Bitter clay

The following thermoplastic resins were used as the thermoplastic polymer used (A).
Ethylene / vinyl acetate copolymer (EVA) manufactured by Tosoh Corporation The vinyl acetate monomer component content is as follows.
EVA-1: 28%
EVA-2: 15%
EVA-3: 6%
Polypropylene (PP) Low density polyethylene (LDPE) manufactured by Nippon Polychem Co., Ltd. Ethylene / ethyl acrylate copolymer (EEA) manufactured by Tosoh Co., Ltd. Polyvinyl chloride (PVC) and polyvinyl chloride compound (manufactured by Nippon Polyolefin Co., Ltd.) PVC-Cp)
Both made by Nihongo Bix Co., Ltd. PVC: DOP: Stabilizer = 100: 50: 2
(B) The following organic compound was used as the surface treatment agent.
Stearic acid Commercially available reagent Copolymer of maleic anhydride and α-olefin Made by Mitsubishi Chemical Co., Ltd. α-olefin has 28 or more carbon atoms (C) Flame retardant additive magnesium hydroxide Kyowa Chemical Industry Aluminum hydroxide manufactured by Nippon Light Metal Co., Ltd. Calcium carbonate manufactured by Sankyo Seimitsu Co., Ltd. Antimony trioxide manufactured by Suzuhiro Chemical Co., Ltd.

Surface treatment of flame retardant The above surface treatment agent was heated to 100C with a thermostat and melted. A part of the above-mentioned clay slaked lime B to D is charged into a super mixer (with a heating jacket) which is a kind of diffusion mixer, heated with stirring, and when the temperature reaches 120 ° C., the above molten surface The treating agent was added and stirred for 30 minutes. While continuing stirring, the mixture was cooled to 60 ° C., and the surface-treated flame retardant was taken out. Thus, the flame retardant of this invention shown in Table 3 was obtained.

Table 3 Flame retardant

Evaluation method The evaluation items of formability and flame retardancy in the following examples are the following two types.
Melt flow rate: JIS K 7210
Unit is g / 10min 230 ℃ × 2.16kg
Oxygen index: JIS K 7201 “Combustion test method for polymer materials by the oxygen index method”
Polymer materials having an oxygen index greater than 21 are less likely to burn in air (oxygen content 21%), and smaller materials are more likely to burn. A polymer material generally called “self-extinguishing” has an oxygen index of 27 or more.

Preparation of test pieces a) Production of test pieces of EVA, PP, LDPE and EEA Polymer and flame retardant were mixed at 180 to 230 ° C using a twin screw extruder, and 190 to 235 ° C using an injection molding machine. To form a strand. Next, it is cut into pellets, put into a mold, heated and melted, and formed into a test piece.
b) PVC
A polymer and a flame retardant are kneaded at 160 ° C. using a mixing roll, and a test piece is molded at 200 ° C. with a manual press molding machine.

Comparative Examples 1-4 and Reference Examples 1-3
Flame retardant EVA was produced by blending flame retardant A, B1 or B2 shown in Table 2 and Table 3 in a proportion shown in Table 4 with respect to EVA-1. For comparison, flame retardant EVA in which commercially available magnesium hydroxide (average particle size 1 μm), aluminum hydroxide or calcium carbonate was blended in the proportions shown in Table 4 was also produced as a reference example . The flame retardancy was evaluated for these, and the following results were obtained.

Table 4 Flame Retardant EVA (Part 1)

When the flame retardant effect is examined with respect to the oxygen index, the value of the flame retardant EVA in which Comparative Example 1, that is, the bituminous slaked lime A is blended, is obtained equivalent to the magnesium hydroxide blended material of Reference Example 2, and Comparative Example 2 and 3, that is, the oxygen index of the flame-retardant EVA blended with the slaked lime B1 or B2 is improved as compared with the EVA of Reference Examples 1 and 2 blended with magnesium hydroxide or aluminum hydroxide. On the other hand, in the case of the calcium carbonate blend of Reference Example 3, almost no flame retardant effect is obtained.

The flame-retarding effect of the present invention is that, in the differential thermal analysis curves shown in FIGS. 1 and 2, the combustion temperature zone of the ethylene / vinyl acetate copolymer and the dehydration / endothermic reaction temperature zone of the bitter slaked lime are very close to each other. Because. When comparing the particle size of the slaked lime lime A and the slaked lime B, the latter particle size is finer than the former, and the higher hydration rate of magnesium oxide contributes to flame retardancy. ing. In particular, the clay slaked lime B2 is surface-treated with stearic acid, so that the dispersibility in the material is improved and the oxygen index in addition to the MFR reaches a further improved level. Thus, the flame retardant of the present invention provides higher flame retardancy to the ethylene / vinyl acetate copolymer compared to known hydroxide flame retardants such as magnesium hydroxide and aluminum hydroxide. Can do.

Examples 1-4
Table 5 shows a case where a flame retardant containing a high-magnesium hydrated lime slaked lime as an active ingredient is blended with EVA-1.

Table 5 Flame Retardant EVA (Part 2)

Comparing Comparative Examples 1 to 3 with Examples 1 and 2 , since the latter used the bituminous slaked lime C having a higher hydration rate of magnesium oxide, the flame retardancy of the flame retardant EVA is further improved. In Examples 6 and 7, a flame retardant EVA having further improved flame retardancy is realized as a result of blending a flame retardant containing, as an active ingredient, mashed slaked lime D having a higher hydration rate of magnesium oxide. In particular, in Example 4 in which the clay-treated lime D2 surface-treated with stearic acid was blended, both the MFR and the oxygen index were improved as a result of improved dispersibility of the flame retardant in the thermoplastic resin. This is the same as that seen in Comparative Example 3.

Examples 5-7 and Comparative Examples 5-7
Unlike EVA-1 above, the vinyl acetate monomer content was examined for the flame retardant effect of highly hydrated mashed slaked lime on EVA-2 and EVA-3, which are 15% and 6%. The results are as shown in Table 6.

Table 6 Flame Retardant EVA (Part 3)

According to the data in Table 6, EVA with a higher vinyl acetate monomer content has a higher flame retardant effect due to highly hydrated clay slaked lime, and EVA with a lower vinyl acetate monomer content has a flame retardant effect. Low. That is, when the flame retardant of the present invention is blended with EVA having a high vinyl acetate monomer content, the significance thereof is even higher. Further, the surface treatment with maleic anhydride / α-olefin copolymer has a higher improvement effect on both MFR and oxygen index than the surface treatment with stearic acid.

Examples 8 to 10 and Comparative Examples 8 to 10
Since D3 was found to be the most effective as a flame retardant, it was blended with polypropylene, low density polyethylene and ethylene / ethyl acrylate copolymer, and the flame retardancy of the resulting flame retardant composition was reduced. Examined. The results are listed in Table 7.

Table 7 Other flame retardant thermoplastic resins

The oxygen index obtained in Examples 8 , 9 and 10 is sufficiently higher than the oxygen index of the thermoplastic resin itself in Comparative Examples 8, 9 and 10, and it is clear that flame retardancy is exhibited. It is. Thus, the flame retardant of the present invention is also effective for thermoplastic resins other than the ethylene / vinyl acetate copolymer.

Example 11 and Reference Examples 4 and 5
The flame retardancy when the flame retardant D3 was added to polyvinyl chloride was compared with the case where a conventional flame retardant was used. The results are as shown in Table 8. The flame slaked lime, which is the flame retardant of the present invention, is more effective than the case where the same amount of aluminum hydroxide is added, and is close to the case where double the amount of antimony trioxide is added. Antimony is one of the rare metals, and antimony trioxide is an expensive flame retardant. As seen in these examples, antimony trioxide can be wholly or partially replaced with mashed slaked lime.

Table 8 Flame retardant polyvinyl chloride

Examples 12-14
The thermoplastic composition was manufactured by changing the ratio of adding the flame retardant D1 to EVA-1 as shown in Table 9, and their moldability and flame retardancy were measured. The results are shown in Table 9. It can be seen that high flame retardancy can be obtained by adding an equivalent or less flame retardant to EVA-1.

Table 9 Flame Retardant EVA (Part 4)

Differential thermal analysis curve of polyolefin materials Differential thermal analysis curve of hydrated metal compounds Electron micrograph of highly hydrated mashed lime D

Claims (3)

A method for producing a flame retardant for a thermoplastic resin or a thermoplastic elastomer, which comprises calcining dolomite, digesting it with water, aging, drying, pulverizing and classifying the powder, and then pulverizing the limestone powder. Digestion,
(A) The water ratio of digested water is in the range of 0.4 to 0.9,
(B) After completion of digestion, the adhesion moisture of the mashed slaked lime when shifting to aging is in the range of 5 to 20% by weight.
And aging is carried out under conditions of an atmospheric temperature of 80 to 120 ° C. and a time of 12 to 48 hours, whereby the hydration rate of magnesium oxide in the mashed slaked lime is 85.7%. The manufacturing method of the flame retardant characterized by the above. The method for producing a flame retardant according to claim 1, wherein the classification is performed so that the primary particle diameter of the clay lime is within a range of 0.5 to 5 µm. Subsequent to the step according to claim 1, at least one kind of surface treatment agent selected from organic acid anhydride / α-olefin copolymer, silane coupling agent and stearic acid is used for the obtained powder of slaked lime. A method for producing a flame retardant comprising subjecting to a surface treatment.

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