DE939954C - Process for the production of shaped bodies, in particular panels from waste wood - Google Patents

Description

- Process for the production of moldings, in particular plates from wood waste The production of chipboard bodies, especially panels of the most varied Thickness and density, from small wood parts such as sawdust, wood shavings, milling shavings, veneer waste, Wood wool, shavings, peat, bark, straw or other lignified annual plants using a wide variety of organic or inorganic binders is known.

From the multitude of organic binders are used today almost exclusively those based on synthetic resins, such as phenol formaldehyde and urea formaldehyde, are used, because the rest of the conditions required in terms of strength and water resistance not enough. Attempts have also been made for a long time to form cellulose compounds to use viscose as a binder, but this has mainly failed because that the sodium hydroxide solution necessary to produce the viscose in the molded body in the course of the Time causes severe fiber damage, efflorescence, discoloration.

Attempts have been made to remedy these disadvantages by adding the viscose and shaping the body the excess caustic soda through an acid precipitation bath is neutralized. In the process, however, the cellulose is precipitated, which makes it the largest Part of the adhesive force of the xanthate is destroyed. The excess lye can can also be washed out with hot water, which also causes precipitation of the Cellulose with the stated disadvantages causes. It is also used for manufacturing known from synthetic horn made of viscose, the viscose before the Coagulation compounds to add heavy metals, alkaline earths or earth metals such as aluminum or zinc oxide, to bind the excess lye through the formation of an aluminate or zincate.

It has also been suggested for wood-like plastics in addition to wood waste (sawdust) and cellulose xanthogenates, their mixture also includes gypsum or add kaolin. Plaster of paris acts as an additional binding agent because with the existing water the well-known gypsum setting and solidification occurs. The finished one Product contains 32010 solid cellulose xanthate, 20010 gypsum, the majority the bond takes over, and 48% sawdust, and temperatures are used during manufacture of 25 ° C is not exceeded.

These known processes have become more detailed due to Studies found that the binding capacity of cellulose xanthates that were produced according to certain proportions and a small proportion of caustic soda, by adding a small, precisely limited amount Hydrate lime can be significantly improved. A procedure was developed for the production of moldings, in particular panels from wood waste, such as sawing, Planing and milling chips, veneer waste, wood wool, peeling chips and peat, bark, Straw or other lignified annual plants using a binding agent, which consists in that a cellulose xanthate mass of cellulose, caustic soda and carbon disulfide in an approximate ratio of 2: 1: 1, with hydrated lime in an amount of 40 to 80 01e of the processed dry cellulose-containing carriers and water mixed with the starting materials to form a paste as a binder is mixed, shaping the body at a temperature between 105 and I80 ° C and a simultaneous short-term adapted to the density to be achieved Pressures up to about 15 atm. takes place and the shaped body then in known Way to be dried.

The binder used according to the invention has the considerable advantage over conventional viscose of extensive reduction or elimination of the free washable sodium hydroxide solution, which in particular prevents the slow decomposition of the lignocellulose, which was previously avoided. In addition, a surprising technical effect is achieved by adding a small amount of hydrated lime to the cellulose xanthate mass. So have z. B. panels made of wood wool, which have been produced in completely the same way once with cellulose xanthate mass alone, another time with additional hydrate lime, significant differences in terms of flexural strength, water absorption, amount of washable caustic soda and inflammability shown, as can be seen from the following table . Plates with plates without Hydrate lime Hydrate lime Volume weight kg / m3 .., 500 500 Flexural strength kg / cm² ........ ..... ..... 120 80 Water absorption in 2 hours ................. 25 to 30 40 to 45 NaOH dissolved by boiling for ½ hour ........ - 3 g / kg plate 6 g / kg plate Volume weight kg / ma 350 350 Panel thickness .. 35 mm 35 mm Burnout time when using a Welding torch. . . 3.5 min. - 1.2 min.

The aforementioned surprising technical effect, which is achieved by adding Hydrated lime to cellulose xanthate is not detectable if held Hydrated lime another Ca compound or other alkaline earth or heavy metal compounds are added to the cellulose xanthate, which clearly shows that hydrated lime is not present as a filler in the molding, but rather the setting process chemically or physically influenced.

Example I60 g of inferior cellulose are mixed with 620 g of I2 ° / Oiger NaOH mixed and left to mature in a known manner, then 80 g of carbon disulfide are added added and also left to stand by a known method. The received however, crumbly, yellow cellulose xanthate mass is not produced in a known manner transformed into viscose by dissolving in NaOH, but with 1620 g of water in 100 g of hydrated lime powder added and stirred to a homogeneous mass. During further processing to form chipboard bodies The following general rule must be observed: 1000 g of wood chips are used with approximately 500 to 1000 g of the above binder, depending on the chip size, intimately mixed, in molds filled and at temperatures between ro5 and 180 ° C at pressures from I to I5 atü, depending on the desired density, pressed for at least 10 minutes and then dried to humidity.

A particle board with a density of 500 kg / m³ is made as follows Manufactured: 1000 g of thin wood waste chips are mixed with 1000 g of binding agent pressed at 1500 C and a pressure of 3 atm for 30 minutes and then 2 Dried hours at 1050 C, with a plate with following properties the following is obtained: density 500 kg / m3, thickness 20 mm, flexural strength 120 kg / cm2, water absorption in 2 hours 27 o / o.

A lightweight board with a volume weight of 350 kg / m3 can be produced are made by mixing 10000 g wood wool with 10000 g binder and pressing at 130 "C with a pressure of I atü for 15 minutes and subsequent drying at 1050 C for 2 hours. The plate then has the following properties: Volume weight 350 kg / m3, thickness 35 mm, flexural strength 50 kg / cm2.

Claims (1)

PATENT CLAIM Process for the production of moldings, in particular Panels made from wood waste, such as sawdust, wood shavings or milling chips, veneer waste, wood wool, Shavings as well as from peat, bark, straw or other woody annual plants using a binder, characterized in that a cellulose xanthate mass from cellulose, caustic soda and carbon disulfide in an approximate ratio of 2: 1: 1, with hydrated lime in an amount of 40 to 8o ole of the processed dry cellulosic carrier materials and water mixed into a pulpy mass as a binder is mixed with the starting materials, shaping the body at one temperature between IO5 and I800 C and at the same time the density to be achieved adapted short-term application of pressure up to about 15 atm. takes place and the molded body are then dried in a known manner. Reference documents: French patent specification No. 771 359.