DD240196A1 - METHOD FOR PRODUCING LIGNOCELLULOSE CEMENT PANELS V - Google Patents

Abstract

The invention relates to a process for the production of lignocellulosic cement boards (hereinafter LCZ boards) for the removal of asbestos cement building boards, in particular by the use of waste paper instead of asbestos. The object of the invention is to produce on the basis of the process steps formation of a suspension of lignocellulosic fibers, especially waste paper and water, admixture of cement, web formation, pressing (as needed) and Aushaerten the plate, a LCZ plate with increased strength and durability properties. According to the invention, the object is achieved by adding 0.1 to 2.0% by weight (based on cement) of potassium or sodium methylsiliconate solution during the preparation phase of the pulp and mixing the cement at the earliest after 20 minutes of action.

Description

Field of application of the invention

The invention relates to a process for the production of lignocellulosic cement boards (hereinafter LCZ boards) for detachment of asbestos cement building boards, in particular by the use of waste paper instead of asbestos.

Characteristic of the known technical solutions

Asbestos cement boards contain 10 to 15% asbestos fibers. They achieve bending strengths between 20 and 40 MPa. It has long been the task to replace the asbestos wholly or at least partially.

In CS-EB 1631-79 this object is achieved by replacing up to 50% of the asbestos fraction with LCF in the form of pulp. These plates achieve surface finish flexural strengths between 25 and 30 MPa at a density of 1.55 g / cm ³ . (Designation: surface-finished jacket panels Ecalit C)

It has also been tried to replace the asbestos by economically cheaper waste paper. According to DE-AS 28 ^ 4506 an asbestos-free shell board is produced in the winding process. Carrier fibers and / or waste paper are ground in a ball mill to 30 to 70 ⁰ SR. The fibers prepared in this way are added to a hydraulic binder at between 3 and 30% per total mass and the plates are produced therefrom. By grinding the fibers or by additional fibers, the strength of the plates should be increased.

Object of the invention

The aim of the invention is. Asbestos in the production of thin cement-bonded surface elements by Lignocellulosefaser ^ in particular waste paper to replace.

Explanation of the essence of the invention

The object of the invention is to produce on the basis of the process steps formation of a suspension of Lignocellulosefaser ^ especially waste paper, and water, admixing of cement, web formation, pressing (as needed) and curing of the plate LCZ plate with increased strength and resistance properties.

According to the invention, the object is achieved by adding from 0.1 to 2.0% by weight (based on cement) of potassium or sodium methylsiliconate solution during the preparation phase of the pulp and admixing the cement at the earliest after 20 minutes of action.

It has been found that as a result of this, as shown in more detail, the strength and resistance properties of the plates can be improved. An LCZ board produced in this way can also be used for external construction when the asbestos fraction is completely replaced by waste paper.

Preferably deratro pulp content should be 8 to 15% by mass (based on cement).

embodiment

4500g cement PZ 1/45 (Rüdersdorf) 500g recycled waste paper, variety I (Colditz) = AP I

50g potassium methylsiliconate solution

The waste paper was suspended in the turbo solvent in 40 to 50 liters of water until complete separation of the fibers with the addition of potassium or sodium methylsiliconate solution. Subsequently, the suspension was divided into four equal parts and mixed after a contact time of 20 min with 1125g of cement. After homogenization of the suspension by stirring four non-woven fabrics were formed on the casting box under vacuum suction, then dehydrated and pressed at a specific pressure of 4.5 MPa for 3.0 hours. The plates thus produced were stored for seven days in a humid climate and tested after 36 days. The following table shows the increases in strength and resistance properties achieved by the use of potassium methylsiliconate solution.

Variant a _bB o _bB E _B E ₈

MPa% GPa%

1. API 20.0 100 12.1 100

2. API and K / ethyl 22.0 110 14.6 120 sil. Solution

3. KiSah 14.4 100 6.8 100

4. KiSahundK-methyl-17.9 125 8.5 125 sil. Solution

Before the test, the specimens were stored in each case 48 hours in normal conditions.

3-F _013x -Is; (% b - flexural strength of plate specimens with

° ^{bB =} 2. bd ^{2 d} "plate thickness = 5 to 7mm

' b ... plate width = 49 to 51 mm

'_ l _s span = 150 mm

^F max - breaking force

4b · GPa

f _th

Eg modulus of elasticity of panel specimens calculated from flexural strength determinations

f _th .... theoretical deflection of the sample upon reaching the breaking load, if between load and deflection

Proportionality is assumed

Residual bending strength of the specimens after 50 freeze-thaw cycles in accordance with TGL 33433/06 Initial state after 50 freeze-thaw cycles

Claims (2)

Invention claim: 1. A process for the preparation of lignocellulosic cement plates by web formation from the suspension, characterized in that the pulp is suspended with the addition of potassium or Natriummethylsiliconat solution, wherein in the suspension 0.1 to 2.0 Ma .-% (based on cement) Potassium or sodium methylsiliconate solution should act on the fibers for at least 20 minutes. 2. The method according to item 1, characterized in that the pulp content is 8 to 15% by weight (based on cement).