CN115231891B

CN115231891B - Production method of glue-free wood particle anti-aging outdoor trestle plate

Info

Publication number: CN115231891B
Application number: CN202210924096.5A
Authority: CN
Inventors: 陈发江
Original assignee: Guizhou Jingmu Building Materials Co ltd
Current assignee: Guizhou Jingmu Building Materials Co ltd
Priority date: 2022-08-02
Filing date: 2022-08-02
Publication date: 2023-08-04
Anticipated expiration: 2042-08-02
Also published as: CN115231891A

Abstract

The invention relates to a wooden plate manufacturing process, in particular to a glue-free wood particle anti-aging outdoor trestle plate production method, which comprises the following specific steps: the modifier polyvinyl butyral is prepared by reacting polyvinyl alcohol and n-butyraldehyde, mildew-proof antibacterial modification is added by using waste wood particles, a part of magnesite reaction principle is utilized, light burned magnesia powder magnesium chloride solution is added to generate magnesite reaction, nano silicon oil silicon powder aluminum phosphate, vinyl acetate, epoxy resin and other additives are added to be mixed, air holes generated after the magnesite reaction are blocked, redundant chloride ions are locked under the synergistic effect of the three, the water permeability is slowed down, the ageing life is prolonged, the advantages of no mildew, no rot and no insect are caused, the price is moderate, the service life of a trestle can reach more than 10 years, maintenance is not needed within three years, and the paint has extremely strong ageing resistance for outdoor trestle.

Description

Production method of glue-free wood particle anti-aging outdoor trestle plate

Technical Field

The invention belongs to the field of material manufacturing improvement, in particular to a wooden board manufacturing process, and particularly relates to a glue-free wood particle anti-aging outdoor trestle board production method.

Background

Wood is the only renewable and recyclable green material in four world raw materials (steel, cement, wood and plastic), and is a complex biological system material which can well treat the environment and realize self diagnosis and adjustment. Under the environment conditions that people are more and more promoted to safely and naturally live, the wood has unique decorative effect, good environmental characteristics and good processing and construction performances, and the wood material is widely used in green buildings and becomes one of important materials for future development of the building industry. At present, the outdoor trestle widely uses wooden trestle, has low cost, beautiful use, convenient design and good application scene. However, due to the fact that outdoor weather is changeable, factors such as strong wind, heavy rain, temperature and humidity changes and insolation and the like, the wooden outdoor trestle has a low service life, and the problem of the using process is frequent and needs to be frequently maintained.

In recent years, widely used outdoor trestle plates have cement-based outdoor trestle plates, but have the defects of inconvenient cracking and deformation construction and the like; the wood plastic deformation has short service life, and can be scrapped about three years; the cost of the anti-mildew and rot maintenance is high, the cost of the Finnish wood is extremely high, the common anti-mildew wood is cracked while being constructed, and the anti-mildew and rot deformation is realized, so that a large amount of maintenance is needed. Therefore, the improvement of the service life of the wooden trestle and the enhancement of the anti-aging capability of the wooden trestle are a great difficulty for current designers.

In summary, the invention discloses a glue-free wood particle anti-aging outdoor trestle plate production method, which adds mildew-proof antibacterial modification to waste wood particles, utilizes a part of magnesite reaction principle, adds light burned magnesia powder magnesium chloride solution to generate magnesite reaction, adds nano silicon oil silicon aluminum phosphate, vinyl acetate, epoxy resin and other additives to mix, and locks redundant chloride ions under the synergistic effect of the three additives after magnesite reaction, thereby slowing down water permeability, prolonging aging life, having the advantages of no mildew, no rot, no worm and the like, having moderate price, having the service life of trestle of more than 10 years, requiring no maintenance within three years, and having extremely strong anti-aging capability for outdoor trestle.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a glue-free wood particle anti-aging outdoor trestle plate production method, which aims to solve the problems in the technical background.

To achieve the above object, the present invention is achieved by the following technical means:

s1, adding wood powder particles into a stirrer, adding clear water while stirring, and stirring until the mixture is uniform;

s2, adding light burned magnesia powder with the purity of 85% into the solution, and mixing the light burned magnesia powder with wood powder particles according to the proportion of 1:0.5, adding and stirring until the materials are uniformly mixed;

s3, synthesizing modifier polyvinyl butyral, namely adding polyvinyl alcohol into a round bottom flask, adding 3 drops of n-butyraldehyde per second by using a constant pressure dropping funnel, and mixing benzene and acetic anhydride according to a mass ratio of 4:1, mixing, namely generating polyvinyl butyral under the condition of taking concentrated sulfuric acid as a water absorbent, and reacting for 5 hours;

s4, continuously stirring and adding a magnesium chloride solution with the Baume degree of 24 to generate a magnesite reaction, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.55:1, adding a modifier: polyvinyl alcohol locking aldehyde, ferrous sulfate and tributyl phosphate, and adding dispersing agent of pentachlorophenol sodium and triethanolamine according to the mass ratio of 1:1:1:1:1, mixing the materials in proportion and then adding the mixture into a stirring solution;

s5, adding 3% of nano silicone oil silicon powder aluminum phosphate, 15% of vinyl acetate, 17% of epoxy resin and other additives into the stirrer, mixing to generate a magnesite reaction, blocking pores generated after the magnesite reaction, locking residual chloride ions, slowing down water permeability, prolonging ageing life, and preparing a stable environment by matching the nano silicone oil with other cations, wherein the nano silicone oil has extremely high water solubility;

s6, continuously stirring and adding a magnesium chloride solution with the Baume degree of 19, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.55:1, a step of;

s7, uniformly stirring and paving the solution on a plate mold, laminating, locking and maintaining for 36 hours by using a 2800 ton cold press, and demolding to obtain a plate;

s8, after maintaining for 7 days, sanding and fixing the plate to be 18mm x 1220mm x 2440mm, and cutting the plate strip with the thickness of 18mm x 1220mm x 200 mm;

s9, drawing four grooves on the surface of the batten, treating primer wood grain surface oil with wear-resistant and corrosion-resistant paint, and polishing for three times to obtain a finished product;

s10, adding 8% of various mixed liquids such as phosphoric acid, sulfuric acid, oxalic acid, boric acid, nitric acid, trinna phosphate and the like to enable the finished board to generate passivation reaction, absorbing carbon dioxide to react with sulfur dioxide, forming new passivation substances on the surface, and generating more substances with longer time, so that the hardness is better.

Preferably, the wood flour particles in step S1 are added to a mixer to achieve a water content of 40%.

Preferably, the wood flour particles in step S1 are added to a mixer to achieve a wood flour moisture content of 20%.

Preferably, in the step S4, a magnesium chloride solution with Baume degree of 18 is added with stirring to generate a magnesite reaction, and the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.75:1.

preferably, in the step S4, a magnesium chloride solution with the Baume degree of 26 is added with stirring to generate a magnesite reaction, and the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.95:1.

preferably, in the step S4, the nano silicon oil silicon powder aluminum phosphate with the mass concentration of 8%, 19% of vinyl acetate, 2% of epoxy resin and other additives are added into a stirrer to be mixed to generate a magnesite reaction.

Preferably, in the step S1, additives such as nano silicon oil silicon powder aluminum phosphate with the mass concentration of 5%, 17% of vinyl acetate, 23% of epoxy resin and the like are added into a stirrer to be mixed to generate a magnesite reaction.

Preferably, in step S5, a magnesium chloride solution with a baume degree of 25 is added with stirring, and the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.95:1.

preferably, in step S5, a magnesium chloride solution with baume degree of 23 is continuously added, and the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.75:1.

preferably, in the step S6, the solution is stirred and evenly paved on a plate mold, and the plate is obtained by laminating, locking and maintaining for 32 hours by using a 3000 ton cold press, and demolding.

Preferably, in the step S6, the solution is stirred and evenly paved on a plate mold, and the plate is obtained by laminating, locking and maintaining for 38 hours by using a 2500 ton cold press, and demolding.

Preferably, in step S9, 5% of a plurality of mixed liquids such as phosphoric acid, sulfuric acid, oxalic acid, boric acid, nitric acid, trinna phosphate and the like are added to enable the finished board to generate passivation reaction.

Preferably, in the step S9, 3% of a plurality of mixed liquids such as phosphoric acid, sulfuric acid, oxalic acid, boric acid, nitric acid, trina phosphate and the like are added to lead the finished board to generate passivation reaction

Compared with the prior art, the invention has the following beneficial effects:

1. the waste wood particles are added with mildew-proof antibacterial modification, and a part of magnesite reaction principle is utilized, and a light burned magnesia powder magnesium chloride solution is added to generate magnesite reaction, so that the aging resistance of the wood trestle is improved.

2. And adding additives such as nano silicon oil silicon powder aluminum phosphate, vinyl acetate, epoxy resin and the like, mixing, blocking air holes generated after the magnesite reaction, and locking redundant chloride ions under the synergistic effect of the three, so as to slow down the water permeability and prolong the aging life.

3. The outdoor trestle has the advantages of no mildew, no decay, no insect resistance and the like, is moderate in price, has the service life of more than 10 years, and has stronger service performance.

4. The trestle plate of vegetation of the invention has good quality and low price, can realize mass production, and has good application prospect.

Drawings

FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of a monomer for preparing polyvinyl butyral according to the present invention.

FIG. 2 is a nuclear magnetic resonance hydrogen spectrum of a monomer for preparing polyvinyl butyral according to the present invention.

FIG. 3 shows the change in the water contents of inventive example 1, comparative example 2 and comparative example 3.

FIG. 4 is a graph showing the residual stress index test change curves of the present invention in example 2, comparative example 6 and comparative example 7.

Fig. 5 is FTIR spectra of three samples obtained by fourier infrared spectroscopy of inventive example 3, comparative example 8 and comparative example 9.

FIG. 6 is SEM microcosmic appearance of cross-section and diametral section of inventive example 2, comparative example 6 and comparative example 7.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The invention provides a glue-free wood particle anti-aging outdoor trestle plate production method, which comprises the following specific steps:

Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.

Example 1

s5, adding 3% of nano silicone oil silicon powder aluminum phosphate, 15% of vinyl acetate and 17% of epoxy resin additive into the stirrer, mixing to generate a magnesite reaction, blocking pores generated after the magnesite reaction, locking residual chloride ions, slowing down water permeability, prolonging ageing life, and preparing a stable environment by matching the nano silicone oil with other cations, wherein the nano silicone oil has extremely high water solubility;

Comparative example 1: in the step S4, the modifier polyvinyl alcohol and ferrous sulfate are not added, and the rest is the same as in the example 1.

Comparative example 2: in the step S4, the dispersing agent sodium pentachlorophenate, triethanolamine and the rest are the same as in the example 1.

Comparative example 3: in the step S5, special silicone oil silicon powder aluminum phosphate is not added, and the rest is the same as in the example 1.

Comparative example 4: in step S5, no vinyl acetate was added, and the other components were the same as in example 1.

Comparative example 5: in step S5, no epoxy resin was added, and the other components were the same as in example 1.

Example 2

s5, adding 5% of nano silicone oil silicon powder aluminum phosphate, 17% of vinyl acetate, 23% of epoxy resin and other additives into the stirrer, mixing to generate a magnesite reaction, blocking pores generated after the magnesite reaction, locking residual chloride ions, slowing down water permeability, prolonging ageing life, and preparing a stable environment by matching the nano silicone oil with other cations, wherein the nano silicone oil has extremely high water solubility;

s10, adding 8% of mixed liquid of phosphoric acid, sulfuric acid, oxalic acid, boric acid, nitric acid and trinaphalocrocis phosphate to enable the finished board to generate passivation reaction, absorbing carbon dioxide to react with sulfur dioxide, forming new passivation substances on the surface, and generating more substances with longer time and better hardness.

Comparative example 6: in the step S4, adding a magnesium chloride solution with the Baume degree of 10 to generate a magnesite reaction, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 1:1, the remainder being the same as in example 2.

Comparative example 7: in the step S4, adding a magnesium chloride solution with the Baume degree of 5 to generate a magnesite reaction, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 3:1, the remainder being the same as in example 2.

Example 3

s5, adding 8% of nano silicone oil silicon powder aluminum phosphate, 19% of vinyl acetate, 2% of epoxy resin and other additives into the stirrer, mixing to generate a magnesite reaction, blocking pores generated after the magnesite reaction, locking residual chloride ions, slowing down water permeability, prolonging ageing life, and preparing a stable environment by matching the nano silicone oil with other cations, wherein the nano silicone oil has extremely high water solubility;

s6, continuously stirring and adding a magnesium chloride solution with the Baume degree of 25, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.95:1, a step of;

Comparative example 8: in the step S2, a light burned magnesia powder having a purity of 95% was added, and the remainder was the same as in example 3.

Comparative example 9: in the step S2, light burned magnesia powder with a purity of 75% was added, and the rest was the same as in example 3.

Example 4

Comparative example 10: isobutanol was added in step S3, and the rest was the same as in example 3.

To evaluate the water content test, residual stress index, corrosion resistance and defect quality of the boards prepared in examples and comparative examples, we conducted the following methods for the relevant tests:

water content detection

The wood boards prepared in the example 1, the comparative example 2 and the comparative example 3 are placed in an outdoor environment, the instant water content is measured and calculated by taking time as an axis by adopting a controlled variable method, after the weight of each experimental test piece is determined, the weight of each water content test piece is rapidly weighed and recorded (the loss of water in the process is avoided as much as possible), and the actual absolute weight of the experimental test piece is calculated. And then the absolute dry weight is estimated by replacement, and the more accurate value of the average water content of each experimental test piece at different moments in the heat-moisture treatment and drying process is obtained. FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of a monomer, and FIG. 2 is a nuclear magnetic resonance hydrogen spectrum of a monomer, and it can be seen that the polyvinyl butyral structure prepared by the reaction of n-butanol. Using the method of synthesizing acetals, carbonyl groups are strongly polar groups, and carbon shows a strong electropositivity, thus facilitating nucleophilic reagent reactions. And the oxygen on the hydroxyl in the alcohol has a lone pair electron and has stronger nucleophilicity, and the oxygen attacks carbonyl carbon by the lone pair electron to form hemiacetal. the-OH groups of the hemiacetals are unstable. The acetal formation reaction proceeds in the forward direction using concentrated sulfuric acid to absorb water. The modifier polyvinyl butyral is prepared by reacting polyvinyl alcohol and n-butyraldehyde, mildew-proof antibacterial modification is added to waste wood particles, a part of magnesite reaction principle is utilized, light burned magnesia powder magnesium chloride solution is added to generate magnesite reaction, nano silicone oil silicon powder aluminum phosphate, vinyl acetate, epoxy resin and other additives are added to be mixed, air holes generated after the magnesite reaction are blocked, redundant chloride ions are locked under the synergistic effect of the three, the water permeability is slowed down, and the aging life is prolonged. Table 1 is the instantaneous water contents of example 1, comparative example 2 and comparative example 3, and fig. 3 is the variation of the water contents of example 1, comparative example 2 and comparative example 3.

TABLE 1 instant moisture content variation of wood (%)

Parameters (parameters)

Before treatment

Post-treatment/0

24h

48h

72h

96h

120h

Example 1

37±0.3

35±0.5

31±0.1

29±0.4

26±0.3

23±0.7

21±0.3

Comparative example 1

37±0.2

35±0.4

30±0.6

27±0.3

25±0.4

22±0.6

20±0.4

Comparative example 2

37±0.6

36±0.6

29±0.4

25±0.5

24±0.2

20±0.1

19±0.3

Comparative example 3

37±0.5

36±0.7

27±0.5

27±0.3

24±0.4

19±0.3

18±0.5

Comparative example 4

37±0.3

35±0.3

30±0.4

28±0.4

23±0.5

20±0.4

19±0.4

Comparative example 5

37±0.4

36±0.9

29±0.6

26±0.1

24±0.6

21±0.3

20±0.1

Residual stress index detection

According to the national standard Cone drying quality (GB/T6491-2012), a fork tooth method is adopted, and a fork tooth stress test piece is cut and manufactured at different stages of the drying process to calculate the residual stress index. The test pieces (10 mm thick) of the residual stress index obtained once a day during the drying process are shown in FIG. 4, which is a comparison of the residual stress index detection change curves of example 2, comparative example 6 and comparative example 7, and it can be seen that the residual stress index is increased after the intermediate treatment, and example 2> comparative example 6> comparative example 7, which shows that the longer the treatment time is, the greater the degree of relaxation of the tensile stress of the surface layer and the degree of recovery of the tensile plastic deformation are. But cannot be handled excessively, otherwise reaction forces are created. After the intermediate treatment, the residual stress index of example 2 recovered most quickly, thus it can be seen that example 2 had the best mechanical properties.

Corrosion resistance performance detection

The plates prepared in example 3, comparative example 8 and comparative example 9 were subjected to corrosion resistance test, and the samples were dried to constant weight in a drying oven at 103℃and weighed and the mass thereof was recorded as W ₁ Then, the mixture is wrapped by gauze and is placed into a pressure steam sterilizer for treatment for 30min under normal pressure, the water content of a sample reaches 50%, the sample is used after being cooled, then, wood blocks are placed into a culture dish full of hyphae by tweezers in an ultra-clean workbench after ultraviolet sterilization, the culture dish is placed into constant temperature and humidity culture, and a corrosion resistance test is carried out for 12 weeks under the conditions of 28 ℃ and 80%RH. Fig. 5 is FTIR spectra of three samples obtained by fourier infrared spectroscopy, and it can be seen that the sample prepared in example 3 has better corrosion resistance. Table 2 shows the weight gain of the plates prepared in example 3, comparative example 7 and comparative example 8 after corrosion, which represents the water absorption of the plates in the corrosion environment, and is another index for measuring the corrosion resistance of the plates, it can be seen that the weight gain rate of the samples prepared in example 3 is the lowest, and the corrosion resistance of example 3 is optimal after 12 weeks of corrosion.

TABLE 2 sample corrosive Environment weight gain conditions

Defect quality inspection

The defect quality detection is carried out by placing the example 2, the comparative example 6 and the comparative example 7 in an outdoor environment, the defect quality index is calculated according to the specification in GB/T6491-2012, and the detection is carried out by adopting a visible defect experiment test piece. Defects are seen as finning and cracking. The main indexes evaluated by the experiment are the cross section and the SEM microcosmic appearance of the diametral section. It can be seen that the cross-sectional and radial surfaces of example 2 are smoother, and that most of the ducts are filled, while some of the composite apertures can be seen, the spiral strip-like walls are smoother. FIG. 6 is SEM microcosmic appearance of cross-section and diametral section of example 2, comparative example 6 and comparative example 7.

A glue-free wood particle anti-aging outdoor trestle plate production method is characterized in that waste wood particles are added with mildew-proof antibacterial modification, a part of magnesite reaction principle is utilized, light burned magnesia powder magnesium chloride solution is added to generate magnesite reaction, nano silicone oil silicon powder aluminum phosphate, vinyl acetate, epoxy resin and other additives are added to be mixed, air holes generated after the magnesite reaction are blocked, redundant chloride ions are locked under the synergistic effect of the three additives, the water permeability is slowed down, the aging life is prolonged, the advantages of no mildew, no decay, no insect fear and the like are achieved, the price is moderate, the trestle service life can reach more than 10 years, maintenance is not needed within three years, and the glue-free wood particle anti-aging outdoor trestle plate has extremely strong anti-aging capability

The above examples merely illustrate specific embodiments of the invention, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that, it should be understood that those skilled in the art should not depart from the spirit and principle of the present invention, any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention are all equivalents to be included in the scope of the present invention.

Claims

1. A production method of an anti-aging outdoor trestle plate without glue wood particles is characterized by comprising the following steps of: the method comprises the following specific steps:

s2, adding light burned magnesia powder with the purity of 85% into the solution, wherein the mass ratio of the light burned magnesia powder to wood powder particles is 1:0.5, adding and stirring until the materials are uniformly mixed;

s4, continuously stirring and adding a magnesium chloride solution with the Baume degree of 24 to generate a magnesite reaction, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.55:1, adding a modifier: polyvinyl alcohol locking aldehyde, ferrous sulfate and tributyl phosphate, and adding dispersing agent of pentachlorophenol sodium and triethanolamine according to the mass ratio of 1:1:1:1:1, mixing the materials in proportion and then adding the mixture into a stirring solution; alternatively, stirring and adding a magnesium chloride solution with the Baume degree of 26 to generate a magnesite reaction, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.95:1, a step of; or stirring and adding a magnesium chloride solution with Baume degree of 18 to generate magnesite reaction, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.75:1, a step of;

s5, adding 3% of nano silicone oil silicon powder aluminum phosphate, 15% of vinyl acetate and 17% of epoxy resin into the stirrer, mixing to generate a magnesite reaction, blocking air holes generated after the magnesite reaction, locking residual chloride ions, slowing down water permeability, prolonging ageing life, and preparing a stable environment by matching the nano silicone oil with other cations, wherein the nano silicone oil has extremely high water solubility;

s8, after maintaining for 7 days, sanding and sizing the plate to obtain a plate with a thickness of 18mm x 1220mm x 2440mm and cutting the plate into strips with a size of 18mm x 1220mm x 200 mm;

s10, adding 8% of mixed liquid of phosphoric acid, sulfuric acid, oxalic acid, boric acid, nitric acid and trisodium phosphate to enable the finished board to generate passivation reaction, absorbing carbon dioxide to react with sulfur dioxide, and forming new passivation substances on the surface.

2. The method for producing the glue-free wood particle anti-aging outdoor trestle plate according to claim 1, which is characterized by comprising the following steps: the wood powder particles are added into a stirrer, so that the water content of the wood powder is 20-40%.

3. The method for producing the glue-free wood particle anti-aging outdoor trestle plate according to claim 1, which is characterized by comprising the following steps: adding nano silicon oil silicon powder aluminum phosphate with the mass concentration of 1%, 13% of vinyl acetate and 15% of epoxy resin into a stirrer, and mixing to generate a magnesite reaction.

4. The method for producing the glue-free wood particle anti-aging outdoor trestle plate according to claim 3, which is characterized by comprising the following steps of: adding 8% of nano silicon oil silicon powder aluminum phosphate, 19% of vinyl acetate and 25% of epoxy resin into a stirrer, and mixing to generate a magnesite reaction.

5. The method for producing the glue-free wood particle anti-aging outdoor trestle plate according to claim 1, which is characterized by comprising the following steps: and (3) continuously stirring and adding a magnesium chloride solution with the Baume degree of 25 into the mixture in the S6, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.95:1.

6. the method for producing the glue-free wood particle anti-aging outdoor trestle plate according to claim 5, which is characterized by comprising the following steps: continuously stirring and adding a magnesium chloride solution with the Baume degree of 23, wherein the weight ratio of the magnesium chloride solution to the magnesium oxide is 0.75:1.

7. the wood manufactured by the method for producing the glue-free wood particle anti-aging outdoor gallery road plate according to any one of claims 1-6.