CN108608711B

CN108608711B - Antibacterial medium-density fiberboard and preparation method thereof

Info

Publication number: CN108608711B
Application number: CN201711492840.4A
Authority: CN
Inventors: 李勇; 高振忠; 侯贤锋; 李锰
Original assignee: Guangzhou Eme Medical Furniture Technology Co ltd
Current assignee: Guangzhou Eme Medical Furniture Technology Co ltd
Priority date: 2017-12-31
Filing date: 2017-12-31
Publication date: 2021-04-20
Anticipated expiration: 2037-12-31
Also published as: CN108608711A

Abstract

The invention provides an antibacterial medium density fiberboard and a manufacturing method thereof, wherein the antibacterial medium density fiberboard comprises an inner antibacterial part and an outer antibacterial part, and under the synergistic action condition of taking a natural antibacterial agent as a main part and an inorganic antibacterial agent as an auxiliary part, the fibers and an adhesive for surface decorative paper impregnation in the board manufacturing process are subjected to antibacterial treatment at the same time, so that the prepared antibacterial medium density fiberboard is high in antibacterial performance, free of toxic decomposition products, environment-friendly and capable of meeting the national standard requirements on the basic physical performance of the medium density fiberboard.

Description

Antibacterial medium-density fiberboard and preparation method thereof

Technical Field

The invention relates to the field of artificial board decorative materials, in particular to an antibacterial medium-density fiberboard and a preparation method thereof.

Background

Along with the rapid development of economy in China, the living standard of people is rapidly improved, and the requirement on the formaldehyde release amount of furniture is strict, namely the formaldehyde release amount reaches the E1 level of the national standard, so that the formaldehyde release amount does not cause harm to the health of human bodies; in addition, the indoor decoration and furniture are required to keep good antibacterial performance in plum rain season and in the places (bathrooms, toilets and kitchens) with high air humidity, and the defects that the surfaces of the decoration and furniture are stained, the mechanical strength is reduced, peculiar smell is generated and indoor air is polluted because bacteria rapidly propagate and grow after the fiberboard is damped are avoided, and in addition, the human health is harmed because the human body contacts the bacteria for a long time; secondly, high antibacterial requirements are provided for the growth of fungus inside the fiberboard caused by internal gaps or damaged surfaces of the fiberboard in the using process, and the antibacterial requirements for furniture are gradually developed towards a more comprehensive and three-dimensional direction.

Therefore, the development of the artificial board with the antibacterial function has great economic, social and ecological benefits. At present, the domestic research on the antibacterial furniture is not enough in components and systems, the common method is to use the melamine resin adhesive as the decorative paper after the coating is soaked to carry out veneering treatment on the artificial board, the coating is a matrix which is not beneficial to the growth of microorganisms, and most resin adhesive coatings have the effect of resisting the microorganisms. The melamine resin forms a closed coating that prevents to some extent the growth of microorganisms on substrates that are prone to the growth of microorganisms. However, some impurities on the surface of the material also support the growth of microorganisms. As in kitchens, microbial contamination is primarily from food debris, which can be easily removed by using easily cleanable surfaces; for example, the working table area of the office table is a part with extremely high contact frequency when people work on a desk, and the skin directly contacts the surface of furniture and repeatedly contacts, thereby creating conditions for the growth of bacteria. Although melamine resin films have some antimicrobial properties, the overall ability is weak and even minor surface damage, such as microscopically small scratches and coating inhomogeneities, can reduce the dust removal ability of the surface, leading to the growth and infestation of microorganisms inside the wood-based panel.

In the face of increasing artificial board yield and utilization rate, the antibacterial ability of common furniture boards is gradually paid attention to and paid attention to by industries and users. In contrast, the treatment method which is more used in the market is to directly add an antibacterial agent in a certain link in the process of manufacturing the fiberboard, for example, the antibacterial agent is mixed with wood powder in advance and then glue is applied or an adhesive is mixed with the antibacterial agent when glue is applied, and the main manufacturing procedures such as a hot pressing process, a manufacturing process and the like are not changed correspondingly, so that although the antibacterial performance of the artificial board is improved, the physical performance of the artificial board is influenced to a certain extent, and the subsequent long-term use of a user is not facilitated; secondly, the current commonly used antibacterial agents in the market still mainly comprise organic antibacterial agents such as quaternary ammonium salts, phenol ethers, organic metals and the like, and although the antibacterial agents have the advantages of high sterilization speed and generally high antibacterial performance, the effective period is short, particularly, decomposition products are often toxic, the antibacterial agents can cause certain energy degree damage to human bodies after long-term contact, and the antibacterial agents are not suitable for being used as future-developed objects. For example, in CN 1292660C and CN 104126611B, organic substances are selected as antibacterial agents, such as cetylpyridinium chloride, 2n acyl isothiazolone in CN 1292660C, isothiazolinone, triclosan, and butyl paraben in CN 104126611B, which have strong antibacterial effects, but still affect the use of users to some extent due to toxicity and irritation, and have potential safety problems.

Aiming at the problems, the invention provides an antibacterial medium-density fiberboard and a preparation method thereof, on one hand, through improving a melamine resin adhesive for veneering impregnation and board making and hot pressing processes, the prepared artificial board can effectively prevent microorganisms such as fungi from multiplying inside and outside, the integral antibacterial capability of the artificial board is improved, and the surface of the artificial board can also keep a good antibacterial effect when being damaged, so that the service life of the artificial board is prolonged; on the other hand, aiming at the antibacterial agent in the current market, the natural antibacterial agent is selected as a main body, the nontoxic inorganic antibacterial agent is selected as an auxiliary body, and the safety and the environmental protection performance of long-term use are greatly improved while effective antibacterial is ensured through the synergistic effect of different antibacterial agents, so that the decomposed products are nontoxic and harmless.

Disclosure of Invention

The patent provides an antibacterial medium density fiberboard and a preparation method thereof, aiming at the problems from the manufacturing process to the complete process of decorative veneering, and the antibacterial medium density fiberboard can ensure the basic mechanical property and simultaneously ensure the ideal antibacterial property of the manufactured artificial board.

The invention has the technical scheme that the antibacterial medium-density fiberboard comprises a core board and decorative paper on two surfaces of the core board, wherein the core board comprises the following raw materials in parts by mass, wherein each 1m of the raw materials are used³The composition of the finished fiberboard comprises: 780 parts of 700-containing fiber, 300 parts of 150-containing phenolic resin adhesive, 3-5 parts of coupling agent, 180 parts of filler, 50 parts of water, 9-15 parts of antibacterial agent and 10% of curing agent; the decorative paper on the two sides of the core board is formed by dipping a specially prepared antibacterial melamine resin adhesive.

The improvement is characterized in that the curing agent is p-methyl benzene sulfonyl chloride with the purity of more than 79 percent.

The improvement is characterized in that the antibacterial agent is dodecyl dimethyl benzyl ammonium chloride.

The improvement is characterized in that the filler is one or more of quartz powder, montmorillonite and kaolin, and the diameter of the solid particles is 0.01-0.1 mm.

The improvement is characterized in that the phenolic resin adhesive is purchased from the market, and the antibacterial melamine resin adhesive is prepared in a laboratory.

The improvement is characterized in that the coupling agent is titanate coupling agent TMC-311.

As an improvement, the antibacterial medium density fiberboard is characterized by comprising the following steps:

(1) preparing an antibacterial melamine resin adhesive;

(2) weighing the raw materials according to the proportion, and simultaneously sending the standby fiber into a drying kiln to dry the moisture content of the fiber to 4-5%;

(3) according to each 1m³Adding 150 portions of phenol adhesive and 300 portions of phenol aldehyde adhesive into the finished fiberboard, and simultaneously adding a coupling agent and an antibacterial agent according to the proportion of 1: 3;

(4) fully mixing the filler and the fibers in a blast oscillator at 60 ℃ for 30min, and then mixing with the mixture obtained in the step (2);

(5) fully and uniformly stirring the fibers mixed in the step (3), and then paving and forming;

(6) sending the paved fiber mixture into a hot press for hot pressing, wherein the hot pressing temperature is 140-150 ℃, keeping the fiber plate blank consistent with the thickness of a gauge with the thickness of 12mm under the pressure by pressurizing, and continuously hot pressing for 20min to obtain a core plate;

(7) and sticking impregnated paper impregnated with the antibacterial melamine resin adhesive on two sides of the core board, and then carrying out hot pressing at the temperature of 170-175 ℃ under the pressure of 6-7MPa for 160 min.

As an improvement, the special antibacterial melamine resin adhesive is characterized by comprising the following steps:

(1) mixing 165-175 parts of 37% formaldehyde solution and 5-8 parts of sodium montmorillonite, adding into a reactor, and sequentially adding 50 parts of water and 8-9 parts of borax under stirring under the condition of pH 4;

(2) gradually adding 170 parts of melamine-150-5, 0.4-0.5 part of triethanolamine and 17991.5 parts of polyvinyl alcohol in the stirring process, and heating to 95 ℃;

(3) after 40min, adding 10-12 parts of 20nm nano-silver, simultaneously cooling to 80 ℃, and continuing stirring;

(4) adding 20% NaOH solution after 80 min;

(5) measuring turbidity after 5min, when turbid precipitation appears in cold water at 15 ℃, adding 5-6 parts of urea, and adding coupling agents, namely 6-8 parts of toluene solution of gamma-mercaptopropyl trimethoxy silane with the volume fraction of 4% and 10-15 parts of dodecyl dimethyl amine ethyl lactone into a reactor step by step, and continuing stirring;

(6) after 10min, adding 10-15 parts of ethylene glycol, carrying out heat preservation reaction at 80 ℃ until the dilution degree in water at 20 ℃ is 1:3, cooling to 70 ℃, adding 50-70 parts of melamine, and continuously stirring;

(7) when the difference reaches the reaction end point within 15min, adding urea accounting for 4.5 percent of the total part;

(8) after the reaction is finished, the temperature is reduced to 25 ℃, and the reaction solution passes through 100-mesh 200 meshes/cm²The screen mesh of (2) is stored.

The invention takes natural antibacterial agent as main material and nontoxic inorganic antibacterial agent as auxiliary material, and prepares the antibacterial medium density fiberboard which has common antibacterial effect from the inside and the outside and is safe and free of toxic products by improving the manufacturing process of the medium density fiberboard and modifying the melamine resin adhesive of the overlay impregnated decorative paper. Researches show that the antibacterial medium-density fiberboard prepared by the invention has the advantages of high antibacterial strength and obvious effect, can simultaneously meet the requirements of antibacterial property and basic performance of boards in QB/T2591-.

Detailed Description

Example 1

Preparation of antibacterial melamine resin adhesive:

(1) mixing 175 parts of 37% formaldehyde solution and 5 parts of sodium montmorillonite, adding the mixture into a reactor, and sequentially adding 50 parts of water and 8 parts of borax under stirring under the condition that the pH value is 4;

(2) gradually adding 150 parts of melamine, 0.4 part of triethanolamine and 17991.5 parts of polyvinyl alcohol in the stirring process, and heating to 95 ℃;

(3) after 40min, adding 10 parts of 20nm nano-silver, simultaneously cooling to 80 ℃, and continuing stirring;

(4) adding 20% NaOH solution after 80 min;

(5) after 5min, measuring turbidity, when turbid precipitation appears in cold water at 15 ℃, adding 5 parts of urea, and gradually adding 6 parts of coupling agent, namely a toluene solution of 4% gamma-mercaptopropyltrimethoxysilane and 15 parts of dodecyl dimethyl aminoethylenolactone into a reactor in sequence, and continuously stirring;

(6) after 10min, adding 10 parts of ethylene glycol, keeping the temperature at 80 ℃ and reacting until the dilution degree in water at 20 ℃ is 1:3, cooling to 70 ℃, adding 50 parts of melamine, and continuing stirring;

The antibacterial medium density fiberboard comprises the following steps:

(1) weighing the raw materials according to the proportion, and simultaneously sending the standby fiber into a drying kiln to dry the moisture content of the fiber to 4-5%;

(2) according to each 1m³Adding 180 parts of phenolic aldehyde adhesive into the finished fiberboard, and simultaneously adding 3 parts of coupling agent and 9 parts of antibacterial agent;

(3) the filler was thoroughly mixed with the fibers in a 60 ℃ forced air shaker for 30min, followed by mixing with the result of step (2).

(4) Fully and uniformly stirring the fibers mixed in the step (3), and then paving and forming;

(5) sending the paved fiber mixture into a hot press for hot pressing, wherein the hot pressing temperature is 140 ℃, keeping the fiber plate blank consistent with the thickness of a gauge with the thickness of 12mm under the pressure by pressurizing, and continuously hot pressing for 20min to obtain a core plate;

(6) and sticking impregnated paper impregnated with the antibacterial melamine resin adhesive on two surfaces of the core plate, and then carrying out hot pressing at the temperature of 170 ℃, the pressure of 6MPa and the time of 160 min.

The antibacterial performance and the physical mechanical performance of the antibacterial medium density fiberboard prepared in the embodiment are tested according to QB/T2591-:

antibacterial property test (Table 1)

Sample treatment: number a is the inner flat of a sterilization plate of 90mm or 100mm diameter;

number B is medium density fiberboard without added antibacterial component, and the size is 50mm multiplied by 50 mm;

number C is a medium density fiberboard added with antibacterial components, and the size is 50mm multiplied by 50 mm;

the detection basis is as follows: QB/T2591-

Detecting strains:

escherichia coli (Escherichia coli) ATCC25922

Staphylococcus aureus (Staphylococcus aureus) A TCC 6538

Escherichia coli (Escherichia coli) A TCC25922

Klebsiella pneumoniae AS1.1736

Table 1 test results:

bacterial strain	Anti-bacterial rate,%
		Escherichia coli	≥99
Staphylococcus aureus	≥99
		Escherichia coli	≥99
Klebsiella pneumoniae	≥99

Particularly, a medium-density fiberboard sample added with an antibacterial component is used for testing the internal antibacterial property of the medium-density fiberboard, and the specific operation steps are as follows: and (3) sampling a sample, marking equidistant knife seams along two diagonal lines of the sample by using a knife, wherein the distance between the knife seams is 5mm, the width is 1.2mm, and the depth is 2.5mm, and then carrying out antibacterial performance test on the treated fiberboard according to the detection methods in QB/T2591-2003 and GB/T4789.2.

TABLE 2 test results

Basic Performance test of the plaques (Table 2)

The detection basis is as follows: GB/T11718-

TABLE 3 test results

	Standard of merit	This example
			Thickness/mm	9-13	9-13
Static bending strength/MPa	26.0	≥73.5
			Modulus of elasticity/MPa	2500	≥2750
Internal bond strength/MPa	0.50	≥1.0
			Water absorption thickness swelling ratio/%)	15.0	4-8
Surface bonding strength/MPa	0.60	≥1.0
			Water content%	4-13	4-5
Density Kg/m³	450-880	750
			Formaldehyde emission mg/100g	≤9.0	≤2mg/g

Example 2

Preparation of antibacterial melamine resin adhesive:

(1) 170 parts of 37% formaldehyde solution and 6 parts of sodium montmorillonite are mixed and added into a reactor, and 50 parts of water and 8.3 parts of borax are sequentially added under stirring under the condition that the pH value is 4;

(2) 155 portions of melamine, 0.4 portion of triethanolamine and 17991.5 portions of polyvinyl alcohol are gradually added in the stirring process, and the mixture is heated to 95 ℃;

(4) adding 20% NaOH solution after 80 min;

(5) after 5min, measuring turbidity, when turbid precipitation appears in cold water at 15 ℃, adding 5 parts of urea, and gradually adding 6 parts of coupling agent, namely a toluene solution of 4% gamma-mercaptopropyltrimethoxysilane and 12 parts of dodecyl dimethyl aminolactone into a reactor in sequence, and continuously stirring;

(6) adding 12 parts of ethylene glycol after 10min, keeping the temperature at 80 ℃ and reacting until the dilution degree in water at 20 ℃ is 1:3, cooling to 70 ℃, adding 55 parts of melamine, and continuing stirring;

The antibacterial medium density fiberboard comprises the following steps:

(2) according to each 1m³Adding 200 parts of phenolic aldehyde adhesive into the finished fiberboard, and simultaneously adding 2 parts of coupling agent and 6 parts of antibacterial agent;

(5) sending the paved fiber mixture into a hot press for hot pressing, wherein the hot pressing temperature is 145 ℃, keeping the fiber plate blank consistent with the thickness of a gauge with the thickness of 12mm under the pressure by pressurizing, and continuously hot pressing for 20min to obtain a core plate;

(6) and sticking impregnated paper impregnated with the antibacterial melamine resin adhesive on two surfaces of the core plate, and then carrying out hot pressing at the temperature of 170 ℃, the pressure of 7MPa and the time of 160 min.

After the experiment is finished, the antibacterial performance and the basic performance of the board of the antibacterial medium density fiberboard obtained in the example 2 are tested by taking the example 1 as a reference, and the result shows that the antibacterial rate of the antibacterial medium density fiberboard obtained in the example 2 is more than or equal to 99 percent, the antibacterial effect is strong, and the basic performance of the board also meets the corresponding standard. Particularly, the antibacterial rate of the antibacterial medium density fiberboard obtained after the board is subjected to slotting treatment is more than or equal to 90 percent, and the antibacterial effect can also be very good when the surface of the board is damaged.

Example 3

Preparation of antibacterial melamine resin adhesive:

(3) cooling to 80 deg.C for 40min and stirring;

(4) adding 20% NaOH solution after 80 min;

The antibacterial medium density fiberboard comprises the following steps:

After the experiment is finished, the antibacterial performance and the basic performance of the board of the antibacterial medium density fiberboard obtained in the example 3 are tested by taking the example 1 as a reference, and the result shows that the antibacterial rate of the antibacterial medium density fiberboard obtained in the example 3 is more than or equal to 90 percent, the antibacterial effect is achieved, and the basic performance of the board also meets the corresponding standard. Particularly, the antibacterial rate of the antibacterial medium density fiberboard obtained after the board is subjected to slotting treatment is more than or equal to 90 percent, and the antibacterial effect can also be very good when the surface of the board is damaged.

Example 4

Preparation of antibacterial melamine resin adhesive:

(4) adding 20% NaOH solution after 80 min;

(5) after 5min, measuring the turbidity, and when turbid precipitation appears in cold water at 15 ℃, adding 5 parts of urea and continuing stirring;

The antibacterial medium density fiberboard comprises the following steps:

After the experiment is finished, the antibacterial performance and the basic performance of the board of the antibacterial medium density fiberboard obtained in the example 4 are tested by taking the example 1 as a reference, and the result shows that the antibacterial rate of the antibacterial medium density fiberboard obtained in the example 4 is more than or equal to 95 percent, the antibacterial effect is strong, and the basic performance of the board also meets the corresponding standard. Particularly, the antibacterial rate of the antibacterial medium density fiberboard obtained after the board is subjected to slotting treatment is more than or equal to 90 percent, and the antibacterial effect can also be very good when the surface of the board is damaged.

Example 5

The antibacterial medium density fiberboard comprises the following steps:

(2) according to each 1m³Adding phenolic glue into finished fiber board280 parts of adhesive, 3 parts of coupling agent and 9 parts of antibacterial agent are added simultaneously;

(5) sending the paved fiber mixture into a hot press for hot pressing, wherein the hot pressing temperature is 150 ℃, keeping the fiber plate blank consistent with the thickness of a gauge with the thickness of 12mm under the pressure by pressurizing, and continuously hot pressing for 20min to obtain a core plate;

(6) sticking impregnated paper impregnated with common melamine resin adhesive on two sides of the core board, and hot-pressing at 175 deg.C under 6MPa for 160 min;

(7) the common melamine resin adhesive can be purchased in the market.

After the experiment is finished, the antibacterial performance and the basic performance of the board are tested on the antibacterial medium density fiberboard obtained in the example 5 by taking the example 1 as a reference basis, and the result shows that the antibacterial rate of the antibacterial medium density fiberboard obtained in the example 5 is more than 70 percent and less than or equal to 85 percent, and the requirement on the antibacterial effect in the standard QB/T2591-. Particularly, the antibacterial rate of the antibacterial medium density fiberboard obtained after the board is subjected to slotting treatment is more than or equal to 92 percent, and the antibacterial effect can also be very good when the surface of the board is damaged.

Example 6

Preparation of antibacterial melamine resin adhesive:

(1) 160 parts of 37% formaldehyde solution and 8 parts of sodium montmorillonite are mixed and added into a reactor, and 50 parts of water and 8.8 parts of borax are sequentially added under stirring under the condition that the pH value is 4;

(2) gradually adding 170 parts of melamine, 0.5 part of triethanolamine and 17991.5 parts of polyvinyl alcohol in the stirring process, and heating to 95 ℃;

(4) adding 20% NaOH solution after 80 min;

(5) after 5min, measuring turbidity, when turbid precipitation appears in cold water at 15 ℃, adding 5 parts of urea, gradually adding 8 parts of coupling agent, namely a toluene solution of 4% gamma-mercaptopropyltrimethoxysilane and 14 parts of dodecyl dimethyl aminolactone into a reactor, and continuously stirring;

(6) adding 14 parts of ethylene glycol after 10min, keeping the temperature at 80 ℃, reacting until the dilution degree in water at 20 ℃ is 1:3, cooling to 70 ℃, adding 65 parts of melamine, and continuing stirring;

The antibacterial medium density fiberboard comprises the following steps:

(2) according to each 1m³Adding 180 parts of phenolic adhesive into the finished fiberboard;

(6) and sticking impregnated paper impregnated with the antibacterial melamine resin adhesive on two sides of the core board, and then carrying out hot pressing at the temperature of 175 ℃, the pressure of 6MPa and the time of 160 min.

After the experiment is finished, the antibacterial performance and the basic performance of the board are tested on the antibacterial medium density fiberboard obtained in the example 6 by taking the example 1 as a reference, and the result shows that the antibacterial rate of the antibacterial medium density fiberboard obtained in the example 5 is more than or equal to 90 percent and meets the requirement on the antibacterial effect in the standard QB/T2591-2003. Particularly, the antibacterial rate of the antibacterial medium density fiberboard obtained after the board is subjected to slotting treatment is more than 50 percent and less than or equal to 75 percent, and the antibacterial effect is basically lost when the surface of the board is damaged.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are intended to be covered by the claims.

Claims

1. The antibacterial medium-density fiberboard comprises a core board and decorative paper on two surfaces of the core board, and is characterized in that the core board comprises the following raw materials in parts by mass, wherein the finished fiberboard obtained by carrying out labor year after every 1m comprises the following components: 780 parts of 700-containing fiber, 300 parts of 150-containing phenolic resin adhesive, 3-5 parts of coupling agent, 180 parts of filler, 50 parts of water, 9-15 parts of antibacterial agent and 10% of curing agent; the decorative paper on the two sides of the core board is formed by impregnating an antibacterial melamine resin adhesive; the curing agent is p-methyl benzene sulfonyl chloride with the purity of more than 79 percent;

the antibacterial melamine resin adhesive is prepared by the following steps:

(1) mixing 165-175 parts of 37% formaldehyde solution and 5-8 parts of sodium montmorillonite, adding into a reactor, and sequentially adding 50 parts of water and 8-9 parts of borax under stirring under the condition that the pH = 4;

(2) 150 portions of melamine-170, 0.4 to 0.5 portion of triethanolamine and 1799 portions of polyvinyl alcohol are gradually added in the stirring process

1.5 parts by weight, and heating to 95 ℃;

(4) adding 20% NaOH solution after 80 min;

(8) after the reaction is finished, the temperature is reduced to 25 ℃, and the reaction product is stored through a sieve of 100-200 meshes/cm 2.

2. An antimicrobial medium density fiberboard according to claim 1, wherein: the antibacterial agent used in the core plate is dodecyl dimethyl benzyl ammonium chloride.

3. An antimicrobial medium density fiberboard according to claim 1, wherein: the filler is one or more of quartz powder, montmorillonite and kaolin, and the diameter of the solid particles is 0.01-0.1 mm.

4. An antimicrobial medium density fiberboard according to claim 1, wherein: the phenolic resin adhesive is obtained by being purchased in the market, and the antibacterial melamine resin adhesive is prepared in a laboratory.

5. An antimicrobial medium density fiberboard according to claim 1, wherein: the coupling agent is titanate coupling agent TMC-311.

6. The method for preparing the antibacterial medium density fiberboard of claim 1, which is characterized by comprising the following steps:

(1) preparing an antibacterial melamine resin adhesive;

(3) according to the method for carrying out the dry bottom hole cultivation in every 1m, adding 300 parts of phenolic adhesive, and simultaneously adding 3-5 parts of coupling agent and 9-15 parts of antibacterial agent according to the ratio of 1: 3;