WO2001033116A1

WO2001033116A1 - Dry method for the manufacturing of asbestos free sealant for fuel injection pump

Info

Publication number: WO2001033116A1
Application number: PCT/EP2000/010840
Authority: WO
Inventors: Vishwanath Vishnu Hegde; Kayickodathu Ramachandran
Original assignee: Robert Bosch Gmbh
Priority date: 1999-11-05
Filing date: 2000-11-03
Publication date: 2001-05-10
Also published as: GB2373300A; GB2373300B; GB0210001D0; DE10085163T1

Abstract

This invention relates to Asbestos Free Sealant material suitable for the use of Fuel injection pumps, to enhance the sealing effect in all critical points.

Description

Complete Specification

DRY METHOD FOR THE MANUFACTURING OF ASBESTOS FREE SEALANT FOR FUEL INJECΗON PUMP

Background of the invention

A sealant is a substance used to seal joints the commonly known type is the asbestos sealant.

This invention relates to Asbestos Free Sealant material suitable for the use of fuel injection pumps, to enhance the sealing effect m all critical points.

Known Prior Art

Currently m fuel injection pumps, Asbestos sealants are being used to seal the critical joints. The sealing agent is expected to hold the lubricating oil inside the pump and possess adequate compression strength, high and low temperature resistance and temperature shock, controlled swelling behaviour m oil, vibration resistance, fuel resistance, etc.

The asbestos s carcinogenic. The disadvantage is that it has adverse effect on human skin and is health hazardous. Object of the invention

The object of this invention is to provide a new sealant, wherein use of Asbestos is eliminated and to make it environment friendly.

It is another object of the invention to arrive at an end product whose quality is better than currently available.

It is another object of the invention, in the context of present trend in the international arena towards elimination of Asbestos in sealant preparation, to prepare Asbestos free sealant .

According to the invention, the enhanced quality of the sealant originates from the composition and also from the controlled process which has been developed by the inventors .

Summary of the Invention

According to the invention, the sheet for sealant is formed by Mixing (Dry Process) and Hot Calendering process. During the process, the necessary ingredients are added in required quantity and sequence while maintaining the process parameters to the specified values.

Description of the Invention

The sealant, according to invention carried out for resolving the aforementioned disadvantages, involves the said process comprising of steps :-

a. Dry mixing (Dry Process) , b. Hot Calendering Process (Dry Process) The process is now described herein below in its broadest scopes and aspect and the possible variant features and characteristics of the invention are described along with equivalent features and characteristics in the preferred embodiment .

Step 1: Mixing & Milling Process

In this process, the natural rubber is masticated by which the material is permanently softened for further mixing with the nitrile rubber in the required ratio. The mastication is carried out at 45 - 50 rpm and pressure 2.3 - 3 bar. With this, the binder, which is a combination of natural and nitrile rubber is ready for use.

Step 2 : Chopping and Mixing Process

The synthetic pulp is chopped to shorten the length by chopping after the fillers are mixed in the required ratio in a mixer for uniform mixing to avoid agglomeration of the pulp which is essential for the smooth, uniform surface finish of the end product. The binder (a mixture of nitrile and natural rubber) & other vulcanising chemicals are mixed and the mixing is continued for 10 mins . at low rpm mode to ensure that a uniform distribution is achieved.

In this process, 2 different compositions are prepared for the manufacture of the sheet as a 3 layer system termed as "XYX" layers where in the "X &. X" are the outer layers having the same composition and the "Y" layer, middle layer or body layer which contributes the major portion of the required thickness in having a different composition. Each mix is prepared separately and made into a dough form by adding Toulene (375 - 400 ml.) and the mixing is continued for 2 -3 mins . For uniform mix. Care is be taken that the temperature does not exceed beyond 35°C to avoid premature reaction of the vulcanizing chemicals .

Step 2 A: Outer layer - Composition

The outer layer in the manufacture of sheet is having the following compositions:

Step 2 B: Inner layer - Composition

The composition of the body layer is more or less in the same line selected for outer layer. The formulation with the following has resulted in a satisfactory end product for the desired application.

Step 3 : Maturation Process

The mixture thus prepared for the outer layer and body layer is allowed for maturation by leaving at room temperature for 24 hours .

Step 4 : Hot Calendering and Sheet forming process Conditions

Roller Temperature 120 - 125°C Roller Speed 14 - 15 M/min Roller Pressure 34 ... 36 bar

A thin layer of (40 ... 50μm) of the outer layer is built by adding small quantity of the mix to the gap uniformly. Once the outer layer is built, the body mix is added uniformly to continue the roller to pick up the mix resulting in the formation of the sheet. The built up thickness is measured at both ends of the roller with thickness gauge. Any variation between the two ends of the roller can be adjusted with the addition of small quantity of solvent, by which the mix is softened. When the thickness reaches about 0.45 mm, a final coat of outer layer is given. When the required 0.5 mm thickness is achieved on the gauge, stop calendering. Cut open the sheet which is in a tubular form.

Step 5 : Cooling Process

The sheets thus formed are pulled off to cool down.

Physical and Mechanical Properties Achieved

Test Procedure

- Moisturize the test specimen and measure the initial thickness within 5s.

- Place the specimen over the table of thickness gauge and lift the measurement base.

Measure volume change after 30s (within 5s)

Record 10 readings after every 30s on an approximate curve (graph)

Report thickness change at 180s (Reported value should be the average of 5 samples)

Important functional properties achieved

- Pressure Tightness : The material developed has shown excellent pressure tightness

property as a sealant of fuel injection pump at the critical joints up to a pressure of 1.5 bar under adverse assembly conditions .

Torque properties : The specified ratio of initial tightening torque to further tightening torque is minimum 0.45. The material developed has always exhibited a ratio higher than 0.8 in all trials with different and severe test conditions (vibration, temperature etc.)

- Temperature resistance : The material possesses good temperature resistance between - 40 °C and + 140 °C without affecting the pressure tightness.

- Vibration resistance : The material developed is able to function without any leakage under conditions of vibration specified for fuel injection pump coupled with elevated temperature up to 100 °C.

Illustration of the Invention

Figure 1 illustrates the sequential processes involved in the invention.

Claims

We claim : -

1. An Asbestos Free Sealant material suitable for use of the fuel injection pumps.

2. A process for preparation of an Asbestos Free Sealant material, wherein said process, comprises of the steps in sequence: -

a. Dry Mixing (Dry Process) b. Hot Calendering Process (Dry Process)

3. A process as claimed in Claim 2 for preparation of an Asbestos Free Sealant material suitable for use of the fuel injection pumps, comprising the steps of, in sequence.

a. subjecting the polymers to mixing and milling process, b. subjecting pulp and fillers to mixing, c. said mixtures of Step 2(a) and 2(b) being combined and mixed, d. preparing the outer and body layer mixture separately with two different compositions, e. subjecting the said mixture to maturation.

SUBSTITUTE SHEET (RULE 25)

4. A process as claimed in Claim 2, for preparation of an Asbestos Free Sealant material suitable for use of the fuel injection pump, wherein Hot Calendering Process (Dry Process), comprising the steps of:

a. subjecting the mixture to calendering so as to form sheet, b. subjecting the said sheets to cooling.

5. The process Claim 2 & 3 , wherein Steps 2a and 3a, polymers are masticated under controlled speed of 45 50 rpm and controlled pressure of 2.3 - 3 bar.

6. The process of Claim 2 & 3 , wherein Steps 2a, 3b and 3c, the pulp and filler are mixed together in mixer for uniform mixing to avoid agglomeration of pulp.

7. The process of Claim 2 & 3 , wherein Step 2d, the outer layer and body layer mixtures are separately prepared with the following compositions :

Outer layer composition

SUBSTITUTE SHEET (RULE 25)

Inner or body layer composition

8. The process of Claim 2 & 3, wherein Steps 2a, 3d and 3e, the mixture is soaked in solvents for 24 hrs at room temperature .

9. The process of Claim 4, wherein Steps 4a and 4b, the sheets thus formed are hand pulled and allowed to cool down at room temperature.

10. The said sheets are of uniform thickness and smoothness

11. The said sheets are of single layer homogeneous material with following physical and mechanical properties:

12. The said sheet when used as a sealant at critical joints of Fuel Injection Pump, provides following functional properties .

- Pressure Tightness : Excellent pressure tightness property as a sealant of fuel

Injection pump at the critical joints up to a pressure of 1.5 bar under adverse assembly conditions.

Torque properties : Initial tightening torque to further tightening torque ratio higher than 0.8 under different and severe test conditions (vibration, temperature etc.) Temperature resistance : Good temperature resistance between -40°C and +140°C without affecting the pressure tightness .

Vibration resistance : The material developed is able to function without any leakage under conditions of vibration specified for fuel injection pump coupled with elevated temperature up to 100°C.