JP2001294467A - Artificial marble molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an artificial marble molded product which is particularly used in a water section water of a house, and to which any fouling matter is hardly stuck. SOLUTION: This artificial marble molded product contains a resin component, an inorganic filler and an additive having lower surface fee energy than that of the resin component, wherein the additive used in organosilicon compound having, at it one terminal, a group reactive with the resin component an by using this additive, artificial marble of which the molded product is excellent in water repellency, oil repellency, antifouling properties, antimicrobial activity and antifungal activity, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial marble, and more particularly to an acrylic artificial marble having excellent stain resistance.

[0002]

2. Description of the Related Art Artificial marble is generally made of resin, inorganic filler,
Consists of low shrinkage agent, catalyst, cross-linking agent, pigment, etc., casting method,
It is formed by a hot press method or the like. (Meth) acrylic artificial marble, in which (meth) acrylic resin is blended with inorganic filler such as aluminum hydroxide, has processability, workability,
It is excellent in warm water resistance, strength, weather resistance, etc., close to natural marble, and has a sense of luxury, so it is used for washing places, counter tops, kitchen tops, sanitary applications, furniture, interior materials, etc. ing.

[0003]

However, the kitchen,
The problem of artificial marble used in places around water such as washrooms and bathrooms is that it tends to get dirty, and bacteria and mold grow on those dirt as feeds, which poses a problem in terms of appearance and hygiene. there were.

[0004]

In order to solve the above problems, the present invention comprises a resin component, an inorganic filler, and an additive of a substance whose surface free energy is smaller than the surface free energy of the resin component. It is a molded artificial marble.

According to the above invention, the surface free energy of the artificial marble molded article is reduced by the effect of the additive having a small surface free energy, the water repellency is improved, and the interaction with the dirt component is reduced. The performance is greatly improved. Also,
When the additive reacts with the resin component, the resin component and the additive are integrated, and the artificial marble molded product itself exhibits water repellency, thereby greatly improving the durability.
Bacteria and mold also have a small amount of adhered dirt components serving as their baits, so that their growth is also suppressed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The artificial marble of the present invention is an artificial marble molded article comprising a resin component, an inorganic filler and an additive of a substance whose surface free energy is smaller than the surface free energy of the resin component. is there. The surface of the artificial marble molded body contains an additive having a small surface free energy, so that the water repellency is improved, the activity of the artificial marble is reduced, and the stain component is less likely to adhere. Bacteria and fungi also have a small amount of adhered dirt components that serve as their baits, so that growth is suppressed.

Further, it is an artificial marble containing an organic silicon compound as an additive. And, by the effect of the extremely low surface free energy of the organic silicon compound, the water repellency of the artificial marble surface can be greatly improved, and the antifouling property of the artificial marble surface is improved.

Further, it is an artificial marble molded article comprising at least one organic silicon compound selected from the group having reactivity with the resin component at one end. The organosilicon compound reacts with the resin component at one end of the reactive group to be integrated. Since they are chemically bonded in a pendant manner, the hydrophobic groups can be oriented more densely near the surface. For this reason, an artificial marble molded product that simultaneously realizes high water repellency and excellent durability becomes possible.

Further, it is an artificial marble formed from at least one selected from the group consisting of melamine (meth) acrylate, glycidyl (meth) acrylate, and methyl (meth) acrylate as the resin component. Also,
It is an artificial marble molded product comprising a mixture of an acrylic monomer and a polymer thereof as a resin component. And, by being composed of these resin component bodies, the artificial marble molded article becomes excellent in physical properties such as mechanical strength, weather resistance and hot water resistance and chemical properties.

[0010] An artificial marble formed from a resin component, an inorganic filler, an organosilicon compound having reactivity with the resin component at one end, and a silane coupling agent. The silane coupling agent reacts and coats the surface of the inorganic filler, further reacts with the resin component, and improves the conformity, and reduces a gap caused by curing shrinkage of the resin component during molding of the artificial marble molded product. This makes it difficult for the dirt component to penetrate and adhere to the gap, and the amount of dirt component adhering is greatly reduced. Further, since the surface of the artificial marble molded article contains an organic silicon compound, the water repellency of the surface of the artificial marble molded article is further improved, the activity of the artificial marble is reduced, and the contamination component is hardly adhered.

Further, the silane coupling agent is an artificial marble molding containing at least one selected from the group which reacts with the resin component and the inorganic filler. Then, the silane coupling agent reacts with the inorganic filler and further with the resin component. As a result, the inorganic filler and the resin component are firmly bonded via the silane coupling agent and are integrated.
As a result, the gap between the inorganic filler and the resin component produced by the curing shrinkage of the resin component during the molding of the artificial marble molded product is reduced, and the penetration and adhesion of the dirt component can be suppressed.

An artificial marble molded and containing a resin component, an inorganic filler, an organic silicon compound reactive with the resin component at one end, and an antibacterial agent, wherein the antibacterial agent is an inorganic antibacterial agent. And an artificial marble formed from at least one organic antibacterial agent. And, by containing an inorganic antibacterial agent, the growth of bacteria mainly causing slime etc. is suppressed. In addition, by containing an organic antibacterial agent, growth of mold is mainly suppressed. The addition of the organosilicon compound reduces the adhesion of dirt components that serve as baits for bacteria and mold, so that a small amount of the inorganic and organic antibacterial agents has a sufficient effect. For this reason, the influence on the physical quenching property and the chemical properties of the artificial marble molded article is small, and an artificial marble molded article having excellent properties can be obtained.

The resin component in the present invention is not particularly limited as long as it is a resin which can be hardened to form an artificial marble, and various monomers and monomer units conventionally known as resin components for artificial marble are used. A mixture of a body and a polymer can be suitably used. For example, melamine (meth) acrylate, glycidyl (meth) acrylate, methyl (meth) acrylate and the like can be mentioned. In this specification, (meth) acryl means acryl and / or methacryl. Specific examples of the (meth) acrylic monomer include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Examples include, but are not limited to, benzyl (meth) acrylate.

Examples of the inorganic filler include aluminum hydroxide, calcium hydroxide, magnesium hydroxide, powdered talc, powdered powder, fine silica, diatomaceous earth, gypsum, powdered glass, clay mineral, powdered chalk, marble, limestone, Aluminum silicate, calcium silicate, borax, calcium sulfite, calcium sulfate, barium sulfate, silicon dioxide, calcined right, titanium oxide, antimony trioxide, clay,
Examples include, but are not limited to, aluminum oxide, calcium carbonate, nickel powder, iron powder, zinc powder, copper powder, iron oxide, glass beads, glass fibers, glass fillers having barium and lead salts, silica gel, and the like. is not.

The additives that can be used in the present invention are not particularly limited as long as they have a surface free energy smaller than that of the resin component. Organic silicon compounds are suitable as additives, and these may be used alone or in a mixture. As the organic silicon compound, as a silicone compound, methyl-dienepolysiloxane, or dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, etc., one end of which is amino-modified, epoxy-modified, carboxy-modified , Carbinol-modified and methacryl-modified ones, but not limited thereto.

As the silane coupling agent in the present invention, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane,
β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,
γ-methacryloxypropylmethyldimethoxysilane,
γ-methacryloxypropyltrimethoxysilane, γ-
Methacryloxypropylmethyldiethoxysilane, 7-
Methacryloxypropyltriethoxysilane, N-β
(Aminoethyl) 7-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropylmethtrimethoxysilane, and the like, but are not limited thereto.

The antibacterial agent according to the present invention includes, as inorganic antibacterial agents, silver nitrate, silver sulfate, silver chloride and the like;
Examples include, but are not limited to, zeolites supporting copper, zinc, or tin, and silica gels supporting silver, copper, zinc, or copper.

Examples of the organic antibacterial agent include phenyl ether derivatives such as 10,10'-oxybisphenoxaarsine, N-haloalkylthio compounds such as cyclofluanide, and 2- (4-thiazolyl) benzimidazole (hereinafter abbreviated as TBZ). Imidazole derivatives, 2,3
Examples include, but are not limited to, quaternary ammonium salts such as 5,6 tetrachloro-4- (methylsulfolyl) pyridine.

[0019]

Embodiments of the present invention will be described below.

(Example 1) 100 parts by weight of a syrup composed of polymethyl methacrylate and methyl methacrylate at a weight ratio of 2: 8, and aluminum hydroxide powder 2
00 parts by weight, tert-butyl peroxymaleic acid 0.5 part by weight, ethylene glycol dimethacrylate 0.5 part by weight, ethylene glycol dimethylcaptoacetate 0.3 part by weight, and methacryl-modified dimethylpolysiloxane 4 parts by weight Were sufficiently stirred and mixed with a kneader. The mixture was inserted into a mold and cured to obtain an artificial marble molded product.

Example 2 100 parts by weight of a syrup composed of polymethyl methacrylate and methyl methacrylate at a weight ratio of 2: 8, and aluminum hydroxide powder 2
00 parts by weight, tert-butyl peroxymaleic acid 0.5 part by weight, ethylene glycol dimethacrylate 0.5 part by weight, ethylene glycol dimethyl captoacetate 0.3 part by weight, and methacryl-modified dimethylpolysiloxane 4 parts by weight And 0.5 part by weight of γ-methacryloxypropylmethyldimethoxysilane as a silane coupling agent were sufficiently stirred and mixed with a kneader. The mixture was inserted into a mold and cured to obtain an artificial marble molded product.

Example 3 100 parts by weight of a syrup composed of polymethyl methacrylate and methyl methacrylate at a weight ratio of 2: 8, and aluminum hydroxide powder 2
00 parts by weight, tert-butyl peroxymaleic acid 0.5 part by weight, ethylene glycol dimethacrylate 0.5 part by weight, ethylene glycol dimethyl captoacetate 0.3 part by weight, and methacryl-modified dimethylpolysiloxane 4 parts by weight And 1 part of silver zeolite and TBZ
0.5 parts by weight was sufficiently stirred and mixed with a kneader. The mixture was inserted into a mold and cured to obtain an artificial marble molded product.

Example 4 100 parts by weight of a syrup composed of polymethyl methacrylate and methyl methacrylate at a weight ratio of 2: 8, and aluminum hydroxide powder 2
00 parts by weight, tert-butyl peroxymaleic acid 0.5 part by weight, ethylene glycol dimethacrylate 0.5 part by weight, ethylene glycol dimethyl captoacetate 0.3 part by weight, and methacryl-modified dimethylpolysiloxane 4 parts by weight And 4 parts of silver zeolite and TBZ
2 parts by weight were sufficiently stirred and mixed with a kneader. The mixture was inserted into a mold and cured to obtain an artificial marble molded product.

Comparative Example 1 100 parts by weight of a syrup composed of polymethyl methacrylate and methyl methacrylate at a weight ratio of 2: 8, and aluminum hydroxide powder 2
00 parts by weight, tert-butyl peroxymaleic acid 0.5 part by weight, ethylene glycol dimethacrylate 0.5 part by weight, and ethylene glycol dimethyl captoacetate 0.3 part by weight were sufficiently stirred and mixed with a kneader. . The mixture was inserted into a mold and cured to obtain an artificial marble molded product.

Comparative Example 2 100 parts by weight of a syrup composed of polymethyl methacrylate and methyl methacrylate at a weight ratio of 2: 8, and aluminum hydroxide powder 2
00 parts by weight, tert-butyl peroxymaleic acid 0.5 part by weight, ethylene glycol dimethacrylate 0.5 part by weight, ethylene glycol dimethyl captoacetate 0.3 part by weight, as a non-reactive organic silicon compound 4 parts by weight of polydimethylsiloxane, 1 part by weight of silver zeolite, and 0.5 parts by weight of TBZ were sufficiently stirred and mixed with a kneader. The mixture was inserted into a mold and cured to obtain an artificial marble molded product.

Comparative Example 3 100 parts by weight of a syrup composed of polymethyl methacrylate and methyl methacrylate at a weight ratio of 2: 8, and aluminum hydroxide powder 2
00 parts by weight, tert-butyl peroxymaleic acid 0.5 part by weight, ethylene glycol dimethacrylate 0.5 part by weight, ethylene glycol dimethyl captoacetate 0.3 part by weight, silver zeolite 1 part by weight and T
0.5 parts by weight of BZ was sufficiently stirred and mixed with a kneader.
The mixture was inserted into a mold and cured to obtain an artificial marble molded product.

The water repellency of the surface of the artificial marble obtained in each of the examples and comparative examples was measured using a contact angle meter (CA manufactured by Kyowa Interface Science Co., Ltd.).
The evaluation was made by measuring the wetting angle of water droplets with a (-Z type). Further, stain resistance was confirmed according to JIS K3370. The comparison of the stain resistance was performed visually, and Comparative Example 2 was performed.
The degree of contamination was evaluated as (△), worse (そ れ), and better (○), and relative evaluation was made. The results are shown in (Table 1).

[0028]

[Table 1]

Next, each of the molded bodies obtained in Example 1 and Comparative Example 2 was subjected to a hot water immersion test at 50 ° C. for 40 hours to test the water repellency durability. The results are shown in (Table 2).

[0030]

[Table 2]

Next, tests were performed on the antibacterial performance and mold resistance of the artificial marble molded articles obtained in each of the examples and comparative examples. The antibacterial performance test is 50 mm from the artificial marble molding
A sample of × 50 mm was cut out, and 1 cc of a bacterial solution (Staphylococcus aureus and Escherichia coli) was added dropwise to each sample and cultured at 37 ° C. for 24 hours. Thereafter, the bacteria were washed out with a sterilized phosphate buffer. The number of the washed viable cells was measured by a pour plate method using a medium for cell count measurement. The results are shown in (Table 3).

[0032]

[Table 3]

In the mold resistance test, each sample (50 × 50 mm) placed on an agar medium was sprayed with a liquid of Asbergillus niger and cultured at 25 ° C. for 7 days. The results are shown in (Table 4).

[0034]

[Table 4]

Further, the slimming resistance of each molded article obtained in each of the examples and comparative examples was evaluated. To the bath water after bathing, 0.02% of normal broth, which is a nutrient of the bacterium, was added to obtain a slimy culture solution. In a culture solution kept at 40 ° C., a test piece cut from the molded body was hung and held for 5 days to allow slime to adhere. The sample surface was actually touched, and a slimy sensory test was performed. Based on the degree of sliminess, it is applied to the four-level evaluation. When almost no sliminess is felt, it is regarded as (◎), when it feels a little, (○), when it feels fairly (△), and when it feels strong, it is (×). Relative evaluation was performed for each. The results are shown in (Table 5).

[0036]

[Table 5]

As is clear from Table 1, the artificial marbles of Examples 1 to 4 have remarkably improved water repellency and improved stain resistance as compared with Comparative Examples 1 to 3. These results revealed that the addition of the organosilicon compound having a reactive group at one end improves the water repellency and stain resistance of the artificial marble molded product.

Further, as is clear from (Table 2), Example 1
The artificial marble molded product of Example 2 was able to obtain better water repellency and durability than Comparative Example 2. From these results, it was possible to improve the water repellency of the artificial marble molded article by adding an organic silicon compound having reactivity with the resin component at one end.

Further, as apparent from Table 3, the artificial marble compacts of Examples 3 and 4 and Comparative Example 3 were obtained in Example 1,
2 and a remarkable antibacterial effect on Staphylococcus aureus and Escherichia coli as compared with the molded articles of Comparative Examples 1 and 2. Since the artificial marble molded product to which the organosilicon compound is added is hard to be stained as a bait for bacteria on the surface, the growth of bacteria is suppressed with a small amount of an antibacterial agent in combination with a silane coupling agent or an inorganic antibacterial agent. Clean and clean artificial marble can be obtained.

As is clear from Table 4, the molded articles of Examples 3 and 4 and Comparative Example 3 have better antifungal performance than the molded articles of Examples 1 and 2 and Comparative Examples 1 and 2. I got it. Molded artificial marble to which an organosilicon compound has been added does not easily adhere to the surface of the surface as a mold bait. Therefore, when used in combination with a silane coupling agent or an organic antibacterial agent, the growth of mold can be suppressed with a small amount of antibacterial agent. A clean and clean artificial marble compact can be obtained.

As is apparent from Table 5, the artificial marble molded product exhibits good anti-slimming properties due to the effects of the organosilicon compound, the silane coupling agent and the inorganic antibacterial agent. The addition of the inorganic silicon compound reduces the amount of dirt components adhering to the surface of the artificial marble molded product, reduces the growth of bacteria that cause slime, and makes it difficult for bacterial dead, which is the direct cause of slime, to adhere to the surface. The slimming property was improved. Furthermore, the addition of a small amount of an antibacterial agent can extremely effectively suppress the occurrence of slime.

[0042]

According to the artificial marble of the present invention, the following effects can be obtained.

An artificial marble molded article containing a resin component, an inorganic filler, and an additive whose surface free energy is smaller than that of the resin component, contains an additive having a small surface free energy. The surface of the marble molded product has improved water repellency, has low activity against dirt components, and is less likely to adhere dirt components. By greatly improving the antifouling property of the surface of the artificial marble molded product, the growth of bacteria and fungi is also suppressed because the amount of adhered dirt components serving as their baits is small.

By using an organosilicon compound as an additive for the artificial marble molded product, it is possible to greatly improve the water repellency with a very small surface free energy effect of the organosilicon compound and with a small amount of addition. The antifouling property of the molded article surface is improved.

The organic silicon compound is at least one selected from the group having reactivity with the resin component at one end. As a result, the organic silicon compound reacts and integrates with the resin component and chemically bonds in a pendant manner, so that the hydrophobic group can be oriented more densely near the surface. For this reason, an artificial marble molded product that simultaneously realizes high water repellency and excellent durability becomes possible.

Further, the resin component is an artificial marble molded product composed of at least one selected from the group consisting of melamine (meth) acrylate, glycidyl (meth) acrylate and methyl (meth) acrylate. Thereby, the artificial marble molded body becomes excellent in physical properties such as mechanical strength, weather resistance, and hot water resistance and chemical properties. And, due to the effect of the extremely low surface free energy of the organosilicon compound, the water repellency of the artificial marble surface can be significantly improved with a smaller amount of addition, and the antifouling property of the artificial marble molded product surface is improved. . Furthermore, the organic silicon compound reacts with and integrates with the resin component, whereby the water-repellent durability, that is, the antifouling durability of the artificial marble molded product is greatly improved.

Further, it is an artificially molded article in which the resin component is a mixture of an acrylic monomer and a polymer thereof.
As a result, the artificial-dali molded article is excellent in texture, and further excellent in physical properties such as mechanical properties, weather resistance and hot water resistance, and chemical properties. And, due to the effect of the extremely low surface free energy of the organosilicon compound, it becomes possible to greatly improve the water repellency of the artificial marbled surface by adding a smaller amount, and the antifouling property of the artificial marble molded body surface is improved. You. Further, the organic silicon compound reacts with and integrates with the resin component, so that the water repellency durability, that is, the antifouling durability of the artificially shaped right molded article is greatly improved.

Further, the artificial marble molded article formed by containing a resin component, an inorganic filler, an organosilicon compound having a reactivity with the resin component at one end, and a silane coupling agent is provided by a silane coupling agent. Reacts and coats the surface of the inorganic filler, further reacts with the resin component, and improves compatibility, and reduces gaps caused by curing shrinkage of the resin component during molding of the artificial marble molded product. This makes it difficult for the dirt component to penetrate and adhere to the gap, and the amount of dirt component adhering is greatly reduced. Further, since the surface of the artificial marble molded article contains an organic silicon compound, the water repellency of the surface of the artificial marble molded article is further improved, the activity of the artificial marble is reduced, and the contamination component is hardly adhered.

Further, since the silane coupling agent is at least one selected from the group which reacts with the resin component and the inorganic filler, the inorganic filler and the resin component are firmly bound via the silane coupling agent, Become one.
As a result, the gap between the inorganic filler and the resin component produced by the curing shrinkage of the resin component during the molding of the artificial marble molded product is reduced, and the penetration and adhesion of the dirt component can be suppressed.

An artificial marble molded article containing a resin component, an inorganic filler, an organosilicon compound having reactivity with the resin component at one end, and an antibacterial agent. The antibacterial agent is an artificial marble formed from at least one inorganic antibacterial agent and at least one organic antibacterial agent. The effect of the extremely low surface free energy of the organosilicon compound can significantly improve the water repellency of the artificial marble right surface, thereby improving the antifouling property of the artificial marble molded product surface. In addition, the organic silicon compound reacts with and integrates with the resin component, whereby the water-repellent durability, that is, the antifouling durability of the artificial marble molded product is significantly improved. Furthermore, by containing an inorganic antibacterial agent, the growth of bacteria which mainly causes slime etc. is suppressed. In addition, by containing an organic antibacterial agent, mold growth is mainly suppressed. In addition, when an organic silicon compound and a silane coupling agent are added, the synergistic effect of the addition of the organic silicon compound and the silane coupling agent reduces the attachment of dirt components which become bacteria and fungi.
Inorganic antibacterial agents and organic antibacterial agents are sufficiently effective when added in small amounts. For this reason, the influence on physical properties and chemical properties of the artificial marble molded article is small, and an artificial marble molded article having excellent properties can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08F 291/00 C08F 291/00 C08J 5/00 CEY C08J 5/00 CEY C08K 3/00 C08K 3/00 5 / 00 5/00 5/541 C08L 33/12 C08L 33/12 33/14 33/14 83/04 83/04 101/00 101/00 C04B 103: 67 // C04B 103: 67 111: 54 111: 54 C08K 5/54 (72) Inventor Akihiro Umeda 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 4F071 AA01 AA33 AA67 AB08 AB17 AB21 AB22 AB24 AB26 AB27 AB28 AB30 AC06 AC12 AC13 AC16 AE17 AE22 AH03 BA03 BB01 BC07 4H011 AA02 BA01 BB09 BB16 BB18 BC16 BC19 DA01 DC11 DF04 DG14 DH02 DH07 4J002 AA001 BG051 BG061 BG071 CP032 CP042 CP052 CP092 CP162 DA076 DA078 DA086 DA106 DA108 DA118 DD0DE DE076 DE076 DE236 DF038 DG046 DG048 DG056 DJ006 DJ008 DJ016 DJ018 DJ036 DJ046 DL006 ED058 EU118 EV218 EV328 EX037 EX067 EX077 FD016 FD188 FD207 4J011 PA03 PA06 PA07 PA08 PA13 PA15 PA26 PA45 PA47 PA99 PB22 PB40 DB02 GA08

Claims (9)

[Claims] 1. An artificial marble molded article comprising a resin component, an inorganic filler, and an additive of a substance whose surface free energy is smaller than the surface free energy of the resin component. 2. An additive comprising an organosilicon compound.
The artificial marble molding according to the above. 3. The artificial marble molding according to claim 2, wherein the organosilicon compound is at least one selected from the group having reactivity with the resin component at one end. 4. The resin component according to claim 1, wherein the resin component is composed of at least one selected from the group consisting of melamine (meth) acrylate, glycidyl (meth) acrylate, and methyl (meth) acrylate. Artificial marble moldings. 5. The artificial marble molded product according to claim 1, wherein the resin component comprises a mixture of an acrylic monomer and a polymer thereof. 6. An artificial marble molded article formed by processing a resin component, an inorganic filler, an organic silicon compound having a reactivity with the resin component at one end, and a silane coupling agent. 7. The artificial marble according to claim 6, wherein the silane coupling agent is at least one selected from the group having reactivity with the resin component and the inorganic filler. 8. An artificial marble formed by molding a resin component, an inorganic filler, an organic silicon compound reactive with the resin component at one end, and an antibacterial agent. 9. The antibacterial agent is at least one of inorganic antibacterial agents.
9. The artificial marble molding according to claim 8, comprising at least one of a seed and an organic antibacterial agent.